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UK GCSE Level Chemistry Notes: The Group 1 Alkali Metals Li Na K etc.

Group 1 ALKALI METALS of the Periodic Table (re-edit)

The physical and chemical properties of the Group I Alkali Metals of the Periodic Table and their compound uses

These notes are written for the highest level of UK GCSE (~US grades 9-10), BUT,  this page can act as a primer for the advanced level study of Group I alkali metals such as lithium, sodium and potassium.

Sub-index for GCSE level page on Alkali Metals

1. Where are the Group 1 Alkali Metals in the Periodic Table? and the significance of their electronic structure

2. General introduction to the Group 1 Alkali Metals

(c) doc b3. What are the important trends down Group 1 Alkali Metals

4. Selected data on the Group 1 Alkali Metals

5. The Reaction of Alkali Metals with cold water

6. Explaining the alkali metal reactivity trend

(c) doc b7. The Reaction of Alkali Metals with Non–metals

8. Some compounds of the alkali metals - formula patterns

9. Uses of alkali metals and their compounds

10. Comparison of Group 1 alkali metals and transition metals

11. The group 1 alkali metals in the context of the reactivity series of metals and implications

12. Learning objectives for UK GCSE level students (US grades 8-10)

Alkali Metals GCSE/IGCSE level multiple choice QUIZ – harder Higher tier

Alkali Metals GCSE/IGCSE level multiple choice QUIZ – easier Foundation tier

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

What next? Associated Pages

email doc brown

This is a BIG website, you need to take time to explore it


Keywords–Links for this revision notes page on alkali metals

boiling points * chlorides * data on elements * density * electron arrangements

explaining reactivity trend  *  hydroxides * melting points * oxides * reaction with oxygen/chlorine

reaction with water * trends * typical properties * untypical properties  * uses


Chemistry notes on the physical properties of the alkali metals – lithium, sodium, potassium, rubidium, caesium (cesium) and francium, The chemical properties of alkali metals, chemical reactions of alkali metals with water, oxygen and chlorine – word equations & balanced equations for the reactions of alkali metals.

The uses of alkali metals – the elements and compounds of the Group 1 Alkali Metals of the Periodic Table e.g. lithium, sodium & potassium etc. Also covered are explaining the group I alkali metal reactivity trend, uses of the alkali metals and alkali metal compounds.

These revision notes on the alkali metals should prove useful for the new AQA, Edexcel and OCR GCSE (9–1) chemistry science courses.


1. Where are the Group 1 Alkali Metals in the Periodic Table?

and the significance of their electronic structure

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1 1H  Note that hydrogen does not readily fit into any group 2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be 5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn
  87Fr 88Ra              
Group 1 Alkali Metals  *  Reactive Metals of Groups 1 and 2  *  Transition Metals

Post-transition metals - diagonally down and across Groups 3 to 6 (52Te is a semi-metal)

The zig-zag 'line' roughly separates metals from non-metals (except 'metallic' Te)

Non-metals - diagonally down and across Groups 3 to 7 (except Te)

The very unreactive Group 0 noble gas non-metals

The Group I Alkali Metals are the first vertical column on the left of the Periodic Table, where you find most of the metallic elements. Therefore an Alkali Metal is the first element on a period from period 2 onwards.

Only the top portion of the periodic table is shown and remember metals tend to be on the left and the alkali metals form the first vertical column. Group 1 Alkali Metals also include the elements caesium/cesium (Cs) and radioactive francium (Fr) below rubidium, but are not shown in the above section of the periodic table.

The alkali metals are so named because they readily react with water to form an alkaline solution of the hydroxide e.g. sodium produced the well known alkali sodium hydroxide.

THINKING AHEAD: From a working knowledge of the position of Group 1 Alkali Metals in the periodic table you should be able to predict the number of outer electrons of a Group 1 Alkali Metal,

possible compound formulae of Group 1 Alkali Metals, reactions and symbol equations of Group 1 Alkali Metals and the probable reactivity of  an Alkali Metal in Group 1 from its position in the periodic table,

Group 1 elements, on the left of the periodic table, and at the start of a period, have one outer electron and so you would expect them to be very reactive metals and readily lose the outer electron to form a singly charged positive ion.,

but the physical properties of group 1 alkali metals as well as their chemical reactions and reactivity trend are also explained.

It is the similarity in electron structure (1 electron in the outer shell) that makes the chemistry of group 1 alkali metals the same – group 1 chemistry!

Note: Using 0 to denote the Group number of Noble Gases is very historic now, since, compounds of xenon are known exhibiting a valency of 8. Because of the horizontal series of elements e.g. like the Sc to Zn block (10 elements), Groups 3 to 0 can also be numbered as Groups 13 to 18 to fit in with the actual number of vertical columns of elements. This can make things confusing, but there it is, classification is still in progress and it is for advanced level students only!, not for GCSE level students!


Electronic structure and reactivity of Group 1 Alkali Metals in the context of their position in the Periodic Table

On reaction metals readily form positive ions in compounds by losing electrons e.g. 

sodium Na – e ===> Na+,

magnesium Mg – 2e ===> Mg2+  

aluminium Al – 3e ==> Al3+ 

These are typical electron changes for metals in groups 1, 2 and 3 and the alkali metals are on the furthest left of the periodic table with on one outer electron and it is on the left-hand side of the periodic table you find the most metallic character.

Metallic elements on the left-hand side of the periodic table quite easily lose their few less strongly held outer electrons giving them a high reactivity in forming positive ions eg groups 1 and 2 readily lose 1 or 2 electrons respectively (as with Na and Mg above) to give an electronically stable noble gas structure with a full shell of outer electrons.

These outer electrons, particularly for the alkali metals, are also shielded by other inner electron shells and farthest from the nucleus and so are less strongly held and need less energy to give positive ions with a full outer shell of electrons.

Its energetically easier for an alkali metal to lose one electrons to form a stable positive ion than gain 7 electrons to form an unstable negative ion with a noble gas structure.

Alkali metals have to lose the least electrons to form a stable positive ion with a noble gas structure, this requires the least energy and makes the group 1 alkali metals the most reactive metals on the left-hand side periodic table.

These points and explanations are elaborated on by looking at the chemical reactions of alkali metals further down the page.

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

2. General introduction to the Group 1 Alkali Metals (see also data table below)

The Alkali Metals form Group 1 of The Periodic Table, and called so because they form oxides and hydroxides that dissolve in water to give alkaline solutions and the alkaline hydroxide is formed when the metals react with water.

Pd metals metals metal ==> non–metal groups
Gp 1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1   He
2 3Li

2.1

Be a short section of the periodic table with group 1 electron arrangements B C N O F Ne
3 11Na

2.8.1

Mg Al Si P S Cl Ar
4 19K

2.8.8.1

Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Alkali metals form the first element of a period, with one outer electron, in any period from period 2 onwards. This outer electron similarity of the alkali metals makes them behave in a chemically similar (e.g. similar formulae) and in a particularly reactive way and is a modern pre–requisite of a set of elements belonging to the same group. BUT their similarity in physical properties and chemical reactions fits in well with Mendeleev's original conception of a group classification.

The single outer electron is easily lost, so alkali metals are very reactive and in their chemical reactions they form a singly charged positive ion e.g. Li+, Na+, K+ etc. and the ions formed have a very stable noble gas electron arrangement.

Some of their physical properties of Group 1 Alkali Metals are typical of metals and some are not so typical of metals.

Although Alkali Metals all have one outer electron and so similar physical and chemical properties, a characteristic of a periodic table group, BUT always watch out for trends down a group too. (c) doc b Overview of Periodic Table

 

Why are the group 1 alkali metals like lithium, sodium and potassium store under oil?

Alkali Metals are so reactive that they must be stored under oil in a well sealed glass container to minimise reaction with the oxygen or water vapour in air. When exposed to air, alkali metals rapidly tarnish as a layer of alkali metal oxide is formed.

Note: Oil is a water repellent and a physical barrier towards air and moisture BUT the alkali metals still gradually corrode as traces of oxygen and water diffuse through the oil to reach the very reactive lumps of alkali metal!

Alkali metals should never be touched with the naked hands or fingers, any sweat on you hand would react with the metal producing heat (burn from exothermic reaction), and skin irritation and blistering from the very strongly corrosive alkaline hydroxide that is formed (see reaction of alkali metals with water).

Apart deliberately doing the reaction with water as a demonstration experiment, all apparatus must be completely dry and solvents must be free of moisture in them.

The group 1 alkali metals are so reactive they can burst into flames spontaneously in air, particularly potassium, rubidium and caesium.

 

In what ways are the group 1 alkali metals like lithium, sodium and potassium typical metals?

Alkali metals are many typical metallic properties: e.g. good conductors of heat and electricity, high boiling points, silvery grey surface (but rapidly tarnished by air oxidation).

When an alkali metal atoms reacts, it loses an electron (oxidation) to form a singly positively charged ion eg Na ==> Na+ + e. In terms of electrons 2.8.1 ==> 2.8 and so forming a stable ion with a noble gas electron arrangement (in this case like neon 2.8).

They tend to readily react with most non–metals to form ionic compounds which are usually soluble white solids.

 

In what ways are the group 1 alkali metals like lithium, sodium and potassium not typical metals?

Alkali metals have several untypical metallic properties: e.g.

low melting points, this means unusually for metals, the bonding between the metal atoms in the crystal is weak.

low density (the first three float on water – lithium, sodium and potassium),

very soft (easily squashed or cut with a knife, extremely malleable) and so they have little material strength.


TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals


3. What are the important trends down Group 1 Alkali Metals

 With increase in atomic number (proton number), down the group for the Alkali Metals ...

(c) doc b==>(c) doc b==> (c) doc b ==> down group 1 alkali metals

... are the important trends to know about the group 1 alkali metals - trends in melting point, boiling point, reactivity, size of atom (atomic radius), density and physical strength as you go down the group with increase in atomic number (proton number) or relative atomic mass.

The melting point and boiling point generally decrease down Group 1 Alkali Metals (see data table below)

All alkali metals are very reactive and the element gets more reactive down Group 1 Alkali Metals with increase in atomic number (explanation), though they all behave in a similar manner – all in the same group!

The atoms get bigger down Group 1 Alkali Metals (as more electron shells are added, see data table below)

Generally the density increases down Group 1 Alkali Metals (see data table below), although the atom gets bigger, there is a greater proportional increase in the atomic mass (see data table).

Generally the physical hardness decreases down Group 1 Alkali Metals, this suggests the metallic bonding gets weaker down the group.

* Note for advanced A level chemistry students:  The bonding in metals involves the attraction between free negative electrons moving between positively ionised metal atoms (M+ ions). As the atomic radius increases the charges (positive nucleus and delocalised electrons) are further apart and the electrical attractive force is reduced. This weaker bonding results in a weaker–softer structure with a lower melting/boiling point.

A Level Chemistry AS–A2 Notes on s–block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

Alkali Metal flame colours

There are element/compound identification details of this and other metal ion tests on the Chemical Tests page (use the alphabetical list at the top).

When heated strongly in a flame, the Alkali metals or their compounds give bright colours.

Simple method for a flame test: The metal salt or other compound  is mixed with concentrated hydrochloric acid and a sample of the mixture is heated strongly in a bunsen flame on the end of a cleaned nichrome wire (or platinum if you can afford it!). Before doing the test the nichrome/platinum wire should be cleaned in conc. hydrochloric acid and heated in the hottest part of the flame to make sure there is no contaminating flame colours.

Lithium – red/crimson (carmine–red)

sodium – yellow/orange

potassium – lilac/purple

rubidium red, caesium – blue

and these flame colours of alkali metals can be used as a simple identification flame test for a specific alkali metal.


Revision notes on the physical and chemical properties of the group 1 alkali metals, chemical reactions of alkali metals, compounds of the alkali metals, explaining the reactivity trend of alkali metals, reactions with water, chlorine and oxygen, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations. Parts or all of these notes are suitable for US grade 8 US grade 9 US grade 10 chemistry

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

more advanced data 4. Selected data on the Group 1 Alkali Metals

Chemical symbol, name of alkali metal

Atomic number of alkali metal Electron arrangement in shells 1, 2, 3 etc. of alkali metal melting point oC, K of alkali metal boiling point oC, K of alkali metal Density g/cm3  of alkali metal atomic radius in nm (nanometre) and pm (picometre)
Li, lithium 3 2.1 181oC, 454K 1347oC, 1620K 0.53 0.157, 157
Na, sodium 11 2.8.1 98oC, 371K 883oC, 1156K 0.97 0.191, 191
K, potassium 19 2.8.8.1 64oC, 337K 774oC, 1047K 0.86 0.235, 235
Rb, rubidium 37 2.8.18.8.1 39oC, 312K 688oC, 961K 1.48 0.250, 250
Cs, caesium 55 2.8.18.18.8.1 29oC, 302K 679oC, 952K 1.87 0.272, 272
Fr, francium 87 2.8.18.32.18.8.1 27oC, 300K 677oC, 950K approx. 2 ~0.280, ~280
GROUP 1 ALKALI METALS Proton number of group 1 alkali metals All group 1 alkali metals have one electron in the outer shell The melting points of group 1 alkali metals decrease down the group. Generally, the boiling points of group 1 alkali metals decrease down the group Alkali metals have low densities, untypical of metals.

Atomic radii increase down the group with each additional electron shell.

Note: For atomic radii: 1nm = 10–9m,  1pm = 10–12m,  nm x 1000 = pm,  nm = pm/1000

Atomic radii always increase down a group with increase in atomic number because extra electron shells are successively added.

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

(c) doc b5. The Reaction of Alkali Metals with cold water

What is formed when group 1 alkali metals like lithium, sodium or potassium react with water? What do you see when the reaction takes place? Observations!

VIDEO of the reaction of group 1 alkali metals with water (from the UK's Royal Society of Chemistry)

Elements – metals on the far left–hand side of the periodic table quite easily lose their outer electrons giving them a high reactivity in forming positive ions. The group 1 alkali metals are the most reactive metal group of the periodic table and only have to lose their one outer electron to form a very stable mono–positive ion with a noble gas electron arrangement.

The Group 1 Alkali Metals are very reactive towards cold water producing hydrogen gas and an alkaline solution of the alkali metal hydroxide.

The reaction of alkali metals with water is very exothermic, fast and violent.

If a lump of the alkali metals lithium, sodium or potassium is placed in cold water, the metal floats, it may melt and move around the surface of the water with 'fizzing'.

Note that these alkali metals float on water because of their low density.

If universal indicator is added, it changes from green (pH 7)  to purple (pH 13–14), showing an alkaline metal hydroxide was formed.

The formation of an alkali with water is why they are called Alkali Metals.

The colourless gas hydrogen is also given off  and pops with lit splint – but this is not the best of experiments to collect it from!

The more reactive the alkali metal, the more vigorous the reaction.

Lithium reacts moderately fast.  Sodium reacts faster.  Potassium reacts very fast.

Rubidium is even faster and caesium is pretty explosive on contact with water.

The clearly observed reactivity trend is:   Li > Na  > K  > Rb  >  Cs

You would NOT do the experiment with francium unless you want to explosively coat the laboratory walls with radioactive isotopes!

Lithium and sodium do not normally cause a flame but the potassium reaction is more rapid exothermic, enough to ignite the hydrogen.

hydrogen + oxygen ==> water   (word equation)

2H2 + O2 ===>  2H2O

2H2(g) + O2(g) ===>  2H2O(l)   (symbol equation with state symbols)

The hydrogen flame turns lilac due to hot potassium atoms in it.

Note 1: In flame tests hot lithium atoms give a  crimson colour and sodium a yellow colour (more details).

Note 2: State symbols in equations: (g) = gas, (l) = liquid, (s) = solid, (aq) = aqueous solution in water

The alkali metals Rubidium, caesium and francium are very explosive with water.

Down group 1 the reaction gets faster and more violent as the alkali metal gets more reactive

i.e. Li < Na < K < Rb < Cs < Fr or francium > caesium > rubidium > potassium > sodium > lithium

The reaction equation for sodium is in words and symbols ...

sodium + water ==> sodium hydroxide + hydrogen    (word equation)

2Na + 2H2O ==> 2NaOH + H2

2Na(s) + 2H2O(l) ==> 2NaOH(aq) + H2(g)   (symbol equation with state symbols)

and the equations are similar for any of the other Alkali Metals since they are in the same group of the Periodic Table, they behave chemically in the same way. On the basis of what you have seen for Li, Na and K, you should therefore be able to predict the reactions and relative reactivity of Rb, Cs and Fr.

i.e. just substitute Li (lithium), K (potassium), Rb (rubidium), Cs (rubidium) or Fr (francium) for Na.

Its handy to know the 'pattern' of both the word equations and symbol equations and it fits in with the idea, an important concept, that elements in the same group of vertical column in the periodic table, all tend to behave chemically in the same way ...

... this is what the Periodic Table is all about!.

e.g. by learning how to write and balance the symbol equation for the reaction between sodium and water, all you have to do is get the symbol of another group 1 alkali metal from your periodic table and deduce the equation i.e. swap Na for a K etc.

potassium + water ==> potassium hydroxide + hydrogen    (word equation)

2K + 2H2O ==> 2KOH + H2

2K(s) + 2H2O(l) ==> 2KOH(aq) + H2(g)   (symbol equation with state symbols)

and

lithium + water ==> lithium hydroxide + hydrogen   (word equation)

2Li + 2H2O ==> 2LiOH + H2

2Li(s) + 2H2O(l) ==> 2LiOH(aq) + H2(g)   (symbol equation with state symbols)

You can predict that the continued reactivity order after Li, Na, K will be K < Rb < Cs < Fr

You can write similar word or symbol equations for rubidium, caesium and francium by replacing Li, Na or K with Rb, Cs or Fr - similar formula and similar balanced equations - all fully predictable without doing any extra experiments!

See RADIOACTIVITY NOTES - symbol for a readioactive substance Theoretically the alkali metal Francium is the most reactive alkali metal and therefore the most explosive metal when in contact with water, however, it is also very radioactive and so the experiment is highly unlikely to be performed!


The explanation of the alkali metals reactivity and reactivity trend is explained and discussed in the next section

See also the Reactivity of Metals Notes for the reactivity of other metals compared to these Group 1 Alkali Metals.


Revision notes on the physical and chemical properties of the group 1 alkali metals, chemical reactions of alkali metals, compounds of the alkali metals, explaining the reactivity trend of alkali metals, reactions with water, chlorine and oxygen, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations. Parts or all of these notes are suitable for US grade 8 US grade 9 US grade 10 chemistry

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

6. Why are alkali metals so reactive? AND

Why do Group 1 Alkali Metals get more reactive down the group with increase in atomic/proton number? How do we explain the group 1 alkali metal reactivity trend?

Pd metals metals metal ==> non–metal groups
Gp 1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp8
1   He
2 3Li

2.1

Be a short section of the periodic table with group 1 electron arrangements B C N O F Ne
3 11Na

2.8.1

Mg Al Si P S Cl Ar
4 19K

2.8.8.1

Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Representations of the electronic changes that accompany the reaction of a group 1 alkali metal.

The atom loses its outer electron to form a very stable ion with the electron configuration of a noble gas.


(c) doc b ==>     +   e

Li   or  [2.1] ==> Li+   or   [2]+   +   e


(c) doc b ==>    +   e

Na  or  [2.8.1] ==> Na+   or   [2.8]+   +   e


(c) doc b ==> + e

K   or   [2.8.8.1]  ==> K+   or   [2.8.8]+   +   e

THEORY  (c) doc b

Explaining the Reactivity Trend of the Group 1 Alkali Metals with water and acids

  • The electronic structure of the alkali metals is the basis for explaining their high reactivity and reactivity order.

  • When an alkali metal atom reacts, it readily loses its only outer electron to form a singly positively charged ion

    • e.g. Na ==> Na+ + e (in terms of electrons 2.8.1 ==> 2.8)

    • and so forming a very stable ion with a noble gas electron arrangement, (see diagrams on left)

    • and this is why they are so reactive,

    • the formation of a positive ion by electron loss is an example of oxidation.

  • AND as you go down the group from one element down to the next

  • .. Li .. Na .. K .. Rb .. Cs .. Fr the atomic radius gets bigger due to the addition of an extra filled inner electron shell,

  • the further a negative electron in the outer shell is from the positive nucleus, the less strongly it is held, hence the more easily lost from an atom to form a positive ion,

  • so, down the alkali metals group, the outer electron is further and further from the nucleus and is also shielded by the extra full shell of negative electron charge,

  • these combined effects mean that down the alkali metal group the outer electron is less and less strongly held by the positive nucleus as the attractive force is decreased, and so ....

  • this means the outer electron is more easily lost in the reaction (e.g. with water), the M+ ion is more easily formed, and so the alkali metal is more reactive as you go down the group.

  • See also 'The Reactivity Series of Metals'

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

7. The Reaction of Alkali Metals with Non–metals

Group 1 Alkali Metals react with non–metallic elements to form colourless or white ionic compounds

These compounds dissolve in water to give colourless solutions.

For these reactions you can often substitute Li (lithium), K (potassium), Rb (rubidium), Cs (caesium/cesium) to obtain the equations for other Group I Alkali Metals.

The reason why they are ionically bonded compounds is that alkali metals readily form positive ions e.g. for sodium

(c) doc b ===>    +   e

Na  or  [2.8.1] ==> Na+   or   [2.8]+   +   e

AND non-metals like oxygen and chlorine also readily form negative ions.

Reaction of group 1 alkali metals with oxygen

VIDEO illustrating the reaction of group 1 alkali metals with oxygen

What is formed when group 1 alkali metals like lithium, sodium or potassium react with oxygen (air)?

Alkali metals burn when heated in oxygen or air – very exothermic reactions.

Unfortunately its a little bit complicated because the principal product, of several possible products, depends on the alkali metal.

They form white solid powders which are ionic compounds eg (Na+)2O2–

sodium + oxygen ==> sodium oxides    (word equation)

4Na + O2 ==> 2Na2O

4Na(s) + O2(g) ==> 2Na2O(s)   (symbol equation with state symbols)

Another oxide is also formed: 2Na + O2 ===> Na2O2 (sodium peroxide)

he diagram below shows the ionic bonding of sodium oxide

(c) doc b + (c) doc b + (c) doc b ==> (c) doc b(c) doc b(c) doc b

These oxides dissolve in water to form strongly alkaline metal hydroxide solutions, pH 13–14, so  universal indicator turns from green to blue.

eg sodium oxide + water ==> sodium hydroxide   (an alkali)

Na2O + H2O ===> 2NaOH

Na2O(s) + H2O(l) ===> 2NaOH(aq)   (symbol equation with state symbols)


Similarly lithium forms lithium oxide: 4Li(s) + O2(g) ===> 2Li2O(s)

and potassium forms potassium oxide: 4K(s) + O2(g) ===> 2K2O(s)

but potassium, like sodium, forms several potassium oxides including:

2K + O2 ===> K2O2   and  K + O2 ===> KO2

(this reaction is more complicated than for lithium, but I wouldn't worry about it at GCSE level!)

and they all dissolve in water to form hydroxides which are very alkaline, pH ~13/14, litmus turns blue, universal indicator turns blue–violet.

See equations for sodium oxide above, just swap Na with Li or K etc.

Reaction with chlorine and other halogens

What is formed when group 1 alkali metals like lithium, sodium or potassium react with chlorine?

VIDEO illustrating the reaction of group 1 alkali metals with chlorine

Alkali metals burn vigorously when heated in chlorine to form colourless ionic salt like compounds eg sodium chloride NaCl Na+Cl. This is a very exothermic reaction AND expensive way to make it! Its much cheaper to produce it by evaporating sea water.

You can do the experiment by heating a small amount of the alkali metal in a deflagrating spoon and plunging into a gas jar of previously prepared chlorine when the metal will burn quite vigorously.

sodium + chlorine ==> sodium chloride    (word equation)

2Na + Cl2 ==> 2NaCl

2Na(s) + Cl2(g) ==> 2NaCl(s)    (symbol equation with state symbols)

(c) doc b the electronic diagram for the ionic bonding in sodium chloride

For more details see Details of the ionic bonding of sodium chloride NaCl

The sodium chloride is an ionic compound, soluble in water to give a neutral solution pH 7, universal indicator is green.

Similarly lithium forms lithium chloride: 2Li(s) + Cl2(g) ==> 2LiCl(s)

and potassium forms potassium chloride: 2K(s) + Cl2(g) ==> 2KCl(s)

All the alkali metals react with all of the halogens to produce white crystalline solids of the ionic compound.

e.g sodium reacts with fluorine gas to give sodium fluoride.

2Na(s)  +  F2(g)  ===>  2NaF(s)

Since the charge on the group 1 metal ions is +1, and the charge on halide ions is -1, its easy to predict the formula of any ionic compound formed between an alkali metal and a halogen i.e. a 1 : 1 ratio.

 

Pd metals Part of the modern Periodic Table

Pd = period, Gp = group

metals => non–metals
Gp1 Gp2 Gp3 Gp4 Gp5 Gp6 Gp7 Gp0
1

1H  Note that H does not readily fit into any group

2He
2 3Li 4Be atomic number Chemical Symbol eg 4Be

Group 1 Alkali Metals and Group 7 Halogens

5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
5 37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
6 55Cs 56Ba Transition Metals 81Tl 82Pb 83Bi 84Po 85At 86Rn

So, you can deduce the following table of all the possible ionic compounds formed from the Group 1 Alkali Metals and the non-metal Group 7 Halogen elements. The matrix below shows you all the possible outcomes of the 1:1 ratio.

Gp1\7 F Cl Br I
Li LiF LiCl LiBr LiI
Na NaF NaCl NaBr NaI
K KF KCl KBr KI
Rb Rb RbCl RbBr RbI
Cs CsF CsCl CsBr CsI

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level  Notes: s–block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

'normal molecular' and ionic formula, M = Li, Na, K etc. 8. Some compounds of the alkali metals - more on formula patterns

Alkali metals are so reactive in readily forming a singly charged positive ion, they usually form ionic compounds, they lose an electron and are NOT interested in sharing it to form a covalent bond!

e.g. the formation of the ionic compound sodium chloride (see above)

ONE (c) doc b atom combines with ONE (c) doc b atom

to form (c) doc b(c) doc b

Alkali metal compounds are usually white solids or colourless crystalline compounds.

For more details see Details of the ionic bonding of sodium chloride NaCl

hydroxides

MOH, M+OH

The hydroxides are white ionic solids which very soluble in water to form strongly alkaline solutions (pH 13–14). See below for salt formation from hydroxides.

oxides, M2O

(M+)2O2–

The oxides are white ionic solids, very soluble in water to form the metal hydroxide (see above).

chlorides

MCl

M+Cl

The chlorides are colourless crystalline solids. They soluble in water to give a neutral solution pH 7, universal indicator is green. They are typical ionic solids with high melting points due to the strong attractive forces between ions (ionic bonding details).

This solution in water consists of sodium Na+ and chloride Cl ions and can be electrolysed to make chlorine, hydrogen and sodium hydroxide.

For more details see Electrolysis of sodium chloride solution (brine)

Formed by neutralising the alkaline oxide or hydroxide with acids (more on Acids, Bases and Salts).

e.g.  word equation and symbol equations

sodium hydroxide + hydrochloric acid ===> sodium chloride + water

NaOH + HCl ===> NaCl + H2O

NaOH(aq) + HCl(aq) ===> NaCl(aq) + H2O(l)   (symbol equation with state symbols)

nitrates

MNO3

M+NO3

Colourless, soluble, neutral crystalline salts, are formed by neutralising the alkaline oxide or hydroxide with nitric acid.

e.g.  word equation and symbol equations

sodium hydroxide + nitric acid ===> sodium nitrate + water

NaOH + HNO3 ===> NaNO3 + H2O

NaOH(aq) + HNO3(aq) ===> NaNO3(aq) + H2O(l) 

(symbol equation with state symbols)

sulfates

M2SO4

(M+)2SO42–

Colourless, soluble, neutral crystalline salts, formed by neutralising the alkaline oxide or hydroxide with sulfuric acid.

e.g.  word equation and symbol equations

sodium hydroxide + sulfuric acid ===> sodium sulfate + water

2NaOH + H2SO4 ==> Na2SO4 + 2H2O

2NaOH(aq) + H2SO4(aq) ==> Na2SO4(aq) + 2H2O(l)  

(symbol equation with state symbols)

carbonates

M2CO3

(M+)2CO32–

White, soluble, weakly alkaline solids formed by reacting the hydroxide with carbon dioxide gas e.g. the formation of sodium carbonate (+ water)

e.g.  word equation and symbol equations

sodium hydroxide + carbon dioxide ===> sodium carbonate + water

2NaOH + CO2 ===> Na2CO3 + H2O

2NaOH(aq) + CO2(g) ===> Na2CO3(aq) + H2O(l)

(symbol equation with state symbols)

Alkali metal carbonates form salts with acids. e.g.

sodium carbonate + hydrochloric acid ===> sodium chloride + water + carbon dioxide

Na2CO3 + 2HCl ===> 2NaCl + H2O + CO2

Na2CO3(s) + 2HCl(aq) ===> 2NaCl(aq) + H2O(l) + CO2(g)  

 (symbol equation with state symbols)

(more details on pH, neutralisation, equations and salt preparations on "Acids, Bases and Salts")

You will find more on theses sorts of equations on ....

GCSE Level Notes on Acids, Bases, Salts and pH scale

Equation Question on Acid reactions – word & symbol equations with answers supplied

Other reactions involving alkali metals or alkali metal compounds

When strongly heated the nitrates of sodium and potassium evolve oxygen gas (ignites glowing splint) and leaving a white residue of the nitrite salt i.e.

sodium nitrate ===> sodium nitrite + oxygen   (word equation)

2NaNO3 ===> 2NaNO2 + O2

2NaNO3(s) ===> 2NaNO2(s) + O2(g) 

(symbol equation with state symbols)

and

potassium nitrate ===> potassium nitrite + oxygen

2KNO3 ===> 2KNO2 + O2

2KNO3(s) ===> 2KNO2(s) + O2(g)

(symbol equation with state symbols)

TOP OF PAGE and sub-index for GCSE Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

9. Alkali Metals – Storylines – USES and ....

sodium Na

Used as a heat transfer coolant in certain nuclear reactors because of its excellent heat conduction properties. The energized vapour is an orange–yellow and used in street lamps.

sodium Na+ salts

Common salt from sea water or underground deposits is sodium chloride, NaCl, and is the raw material for making sodium, hydrogen, chlorine and sodium chloride by electrolysis (see Group 7 Halogens notes).

'Soluble Aspirin' is the sodium salt of an organic acid. Salts of solid organic acids are usually more soluble than the acid itself. 

Sodium hydrogen carbonate  NaHCO3

Sodium hydrogencarbonate's old name is sodium bicarbonate, often referred to as 'bicarb', is used in baking soda, pharmaceutical products like indigestion tablets and fire extinguishers. 

Sodium hydroxide NaOH

An industrially important alkali used in the manufacture of soaps, detergents, salts of acids (see Aspirin above), paper and ceramics.

   

For more on uses of metals see Transition Metals

and Extra notes on industrial chemistry GCSE/IGCSE notes


10. Comparison of Group 1 alkali metals and transition metals

  • Transition metals have much higher melting points than group 1 elements – stronger metallic atomic bonding.
  • Transition metals have higher densities than group 1 alkali metals, non of them float on water!
  • Transition metals are stronger and harder than group 1 metals due to stronger metallic bonding
  • Transition metals are less reactive than group 1 alkali metals towards oxygen, water and halogens like chlorine.
  • Transition metals form coloured ions with different charges, hence different coloured compounds (eg blue copper sulfate solution, brown iron oxide rust etc.).
  • Group 1 alkali metals have only one outer electron, that is easily lost, and so form only one stable ion and they are colourless ions (think of the salts like sodium chloride).
  • Transition metals have more than one electron in the outer shell and more of these electrons can be involved in bonding so they form more than one ion, most of which are coloured.

11. The group 1 alkali metals in the context of the reactivity series of metals and implications for their extraction

Reactivity series of metals - method of metal extraction - relative ease of oxidation reaction with acids

The group 1 alkali metals are the most reactive members of the reactivity series of metals.

For more details see The Reactivity Series of Metals

One consequence is that they cannot be cheaply extracted by reducing their compounds with carbon.

The expensive process of electrolysis must be used.

For the details see Extraction of Aluminium and Sodium


12. Learning objectives for UK GCSE level students (US grades 8-10)

BUT useful revision for higher level courses Advanced A Level  Notes on Group 1 Alkali Metals

Learning objective for the chemistry of the group 1 alkali metals (UK GCSE, IGCSE and US grade 9-10 level)

Know where the alkali metals are in the periodic table - 1st vertical column.

Know they are called the alkali metals because their reaction with water forms an alkali.

Know the typical physical properties of alkali metals.

Know the full electron structure of Li, Na and K, and know the rest of the alkali metals have one electron in the outer shell.

Know that on reaction, alkali metals readily lose one electron to form a singly charged positive ion.

Be able to argue why alkali metals readily lose electrons.

Know the following important group trends down the group 1 alkali metals

Increase in reactivity and be able to explain it in terms of increasing numbers of filled inner shells of electrons and increasing ease of losing an electron

increase is radius of atom with increase in electron shells

generally decreasing melting point and boiling point

low but increase in density, and know Li, Na and K float in water (density < 1.0 g/cm3)

Know alkali metals are stored under oil to reduce reaction with moisture and oxygen in the air.

Know the alkali metals give characteristic flame colours that can be used as a simple identification test

Be able to write word equations and balanced symbol equations for the reaction of alkali metals with water.

Know the reaction between alkali metals and oxygen produces oxides that dissolve in water to form alkaline hydroxides.

Know the reaction of alkali metals with halogens to form salt-like ionic compounds.

Be able to describe, with electronic diagrams, the ionic bonding of the oxides and chlorides of alkali metals.

Be able to predict the simple formulae of the compounds formed between alkali metals and halogens like chlorine.

Know that the alkali metals hydroxides are neutralised by acids to form salts e.g. chlorides, sulfates and nitrates/

Be able to compare and contrast the relative properties of transition metals and alkali metals.

Video summarising the reactions of group 1 alkali metals (from the UK Royal Society of Chemistry) used in GROUP 1


See also Advanced A Level  Notes on s–block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

BUT this page can act as a primer for the study of alkali metals lithium, sodium, potassium etc.


What next? Associated Pages

GCSE Level (~US grades 8-10) School Chemistry Notes (students age ~14-16)

Find your GCSE science course for more help links to revision notes

Advanced Level (~US grades 11-12) pre-university Chemistry Notes (for aged ~17-18)Email doc brown - comment? query?

PLEASE NOTE that these LINKS are for Advanced A Level Chemistry Students ONLY

ADVANCED LEVEL INORGANIC CHEMISTRY Part 7 s–block Gp 1 Alkali Metals/Gp 2 Alkaline Earth Metals  sub–index: 7.1 Introduction to s–block Group 1 Alkali Metals and Group 2 Alkaline Earth Metals  * 7.2 Group 1 data and graphs * 7.3 Group 2 data and graphs * 7.4 General trends down groups I & II and formulae *7.5 Oxygen reaction & oxides of s–block metals * 7.6 Water reaction & hydroxides of group 1/2 metals * 7.7 Acid reaction & salts of group1/2 metals * 7.8 chlorine reaction & halide of group I/II metals * 7.9 carbonates & hydrogen carbonates of s–block metals * 7.10 Solubility trends of groups 1/2 OH, NO3,SO4,CO3 compounds * 7.11 Thermal decomposition and stability of group 1 and group 2 carbonates & nitrates * 7.12 Uses of s–block Group 1 Alkali Metals and Group 2 Alkaline Earth Metals and their compounds

See also Advanced Level  Notes on s–block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

Website content © Dr Phil Brown 2000+. All copyrights reserved on Doc Brown's Chemistry revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries & references to science course specifications are unofficial.  Doc Brown's Chemistry KS4 science GCSE and US grade 8-10 level Chemistry Revision Notes on Group 1 Alkali Metals. Doc Brown's chemistry revision notes: basic school chemistry science GCSE chemistry, IGCSE  chemistry, O level & ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old science students for national examinations in chemistry Revision notes on the physical and chemical properties of the group 1 alkali metals, chemical reactions of alkali metals, compounds of the alkali metals, explaining the reactivity trend of alkali metals, reactions with water, chlorine and oxygen, help when revising for AQA GCSE chemistry, Edexcel GCSE chemistry, OCR GCSE gateway science chemistry, OCR GCSE 21st century science chemistry GCSE 9-1 chemistry examinations.  Parts or all of these notes are suitable for US grade 8 US grade 9 US grade 10 chemistry

What next? Associated Pages

TOP OF PAGE and sub-index for GCSE level Alkali Metals page

See also Advanced A Level Chemistry Notes: s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals