INORGANIC Part 4
Period 2 survey sub-index : 4.1 Period 2 Survey of the
individual elements : 3. lithium :
4. Beryllium
:
5. Boron :
6. Carbon :
7. Nitrogen
:
8. Oxygen :
9. Fluorine
:
10. Neon * 4.2
Period
2 element trends and explanations of physical properties * 4.3 Period 2 element trends in bonding,
structure, oxidation state, formulae & reactions
Advanced
Level Inorganic Chemistry Periodic Table Index *
Part 1
Periodic Table history
* Part 2
Electron configurations, spectroscopy,
hydrogen spectrum,
ionisation energies *
Part 3
Period 1 survey H to He *
Part 4
Period 2 survey Li to Ne * Part
5 Period 3 survey Na to Ar *
Part 6
Period 4 survey K to Kr and important trends
down a group *
Part 7
s-block Groups 1/2 Alkali Metals/Alkaline Earth Metals *
Part 8
p-block Groups 3/13 to 0/18 *
Part 9
Group 7/17 The Halogens *
Part 10
3d block elements & Transition Metal Series
*
Part 11
Group & Series data & periodicity plots
Survey
of Period
2: Li across to Ne (8 elements, Z = 3
to 10)
4.3 Period 2 trends in bonding, structure, oxidation
state, formulae and reactions
M+
X- ionic bond, Mδ+-Xδ+
polar bond and M-X a relatively
non-polar bond (no partial charges shown)
Element |
Lithium |
Beryllium |
Boron |
Carbon |
Nitrogen |
Oxygen |
Fluorine |
Neon |
old/latest Group |
1 |
2 |
3/13 |
4/14 |
5/15 |
6/16 |
7/17 |
0/18 |
ZSymbol
|
3Li |
4Be |
5B |
6C |
7N |
8O |
9F |
10Ne |
Structure of element |
solid
metallic lattice of Li+ and free e- |
solid
metallic lattice of Be2+ and free e- |
solid
giant covalent lattice Bn |
solid
giant covalent lattice Cn |
small gaseous covalent diatomic molecule N2 |
small
gaseous covalent diatomic
molecule O2 |
small
gaseous covalent diatomic
molecule F2 |
gaseous single atoms |
Electron configuration |
1s22s1 |
1s22s2 |
1s22s22p1 |
1s22s22p2 |
1s22s22p3 |
1s22s22p4 |
1s22s22p5 |
1s22s22p6 |
common oxidation states in compounds e.g. in oxides,
chlorides, hydrides |
+1
max +1 |
+2
max +2 |
+3
max +3 |
+4, (+2 in CO,
-4 to +4 in organic compounds)
max +4 |
-1
to +5 (max), -3, +3 & +5 most common
max +5 |
-2,
-1,
+2 in F2O max
+2 |
-1 |
- |
Electronegativity of element |
0.98 |
1.57 |
2.04 |
2.55 |
3.04 |
3.44 |
3.98 |
4.84 |
Formula of oxides |
Li2O |
BeO |
B2O3 |
CO2
(CO) |
N2O,
NO, N2O3, NO2, N2O5 |
O2,
O3 |
F2O |
- |
Bonding and structure of
oxides |
ionic lattice |
ionic lattice with covalent character |
giant covalent lattice |
gaseous small covalent molecules |
gaseous small covalent molecules |
gaseous small covalent molecules |
gaseous small covalent molecule |
- |
electronegativity difference X-O (O
is 3.44) nature of bond |
2.46
Li+ O2- |
1.87
Beδ+-Oδ- |
1.40
Bδ+-Oδ- |
0.89
δ+C=Oδ- |
0.44
Nδ+-Oδ- |
0.00
O-O |
0.54
Oδ+-Fδ- |
- |
Formula of chlorides |
LiCl |
BeCl2 |
BCl3 |
CCl4 |
NCl3 |
Cl2O
or OCl2 |
ClF
or FCl |
- |
bonding and structure of
chlorides |
ionic lattice |
layered covalent lattice |
small covalent gaseous molecule |
small covalent liquid molecule |
small covalent liquid molecule |
non-polar small covalent gaseous
molecule |
small covalent gaseous molecule |
- |
electronegativity difference X-Cl
(Cl is 3.16) nature of bond |
2.18
Li+ Cl- |
1.29
Beδ+-Clδ- |
1.12
Bδ+-Clδ- |
0.61
Cδ+-Clδ- |
0.12
N-Cl |
0.00
Cl-Cl |
0.82
Clδ+-Fδ- |
- |
Formula of hydride |
LiH |
BeH2 |
BH3?,
B2H6 etc. |
CH4 |
NH3 |
H2O
or OH2 |
HF
or FH |
- |
bonding and structure of hydride |
ionic
lattice |
layered covalent polymer lattice |
small covalent gaseous molecule |
small covalent gaseous molecule |
polar small covalent gaseous molecule |
polar small covalent liquid molecule |
polar small covalent gaseous molecule |
- |
electronegativity difference X-H (H is 2.20) nature of bond |
1.22
Li+ H- |
0.63
Beδ+-Hδ- |
0.16
B-H |
0.35
C-H |
1.02
Nδ--Hδ+ |
1.24
Oδ--Hδ+ |
1.78
Hδ+-Fδ- |
- |
********************** |
************ |
*************** |
*************** |
*************** |
*************** |
*************** |
************** |
************ |
-
The
structure and physical properties of the elements:
-
The trend is metal
lattice ==> giant covalent structure ==> small covalent
molecules.
-
Lithium and beryllium are silvery
solids, with a metal lattice structure, and are good conductors of
heat/electricity due to the delocalised free electrons moving
between the immobile metal ions.
-
Boron Bn and
carbon Cn
have a non-metallic giant covalent structure (where n is a very
large number indeed) and are poor conductors of heat/electricity (though
Cn(graphite) shows some metallic character as a
'moderate' conductor). The strong 3D bonding gives boron and
carbon (diamond) very high melting/boiling points and great
hardness.
-
Actually, the diamond/graphite allotropes of carbon
sublime at temperatures over 3500oC. Graphite with
its huge 2D planes of atoms also has a very high melting/boiling
point, though it is physically weak because the 2D layers of
carbon atoms are only held by weak intermolecular forces and
slip over each other under stress
-
Nitrogen N2,
oxygen O2 and fluorine
F2 have a simple-small covalent molecule structure and
neon consists of single atoms. The molecules are only held together
by the weakest of the intermolecular forces, namely the
instantaneous dipole - induced dipole forces, and consequently have
very low melting/boiling points.
-
-
-
Electron configuration
and oxidation states
-
Electron
configurations
of
2,1 or 1s22s1 to 2,8 or 1s22s22p6
-
Filling the s
orbital (max 2 e-'s) gives the metallic s-block elements of
Groups 1-2,
-
filling the p orbitals gives the predominantly
non-metallic p block elements of Groups 3-7 & 0 (13-18) for
Period 2.
-
Oxidation states
in compounds (numerically = valency) are: Li (+1 only), Be (+2
only), B (+3 only), C (usually +4*),
N (-3, +1 to +5), O (usually -2, but can be -1 and +2), F (-1
only), Ne has no stable compounds due to the full outer quantum
level (shell) being full, conferring extra electronic stability on
the atom.
-
From Li to N the
maximum oxidation state is equal to the 'old' group number and the
'highest' oxide formulae can be predicted up to N and the
chloride formula up to C (period 2 elements cannot exceed a
co-ordination number of 4 due to valance orbital restrictions,
in periods 3-4 the maximum is raised to 6.
-
So in the
'highest' oxides you can go from +1 to +5 for Groups 1
to 5, then drops to +2 for fluorine
-
Li2O,
BeO, B2O3, CO2, N2O5 using
all available 1-5 outer 2s and 2p valence electrons,
lastly F2O
-
and the
chloride formula is derived from oxidation state +1 to +4 for Groups 1 to 4/14
(1-4 outer valency electrons),
then declines +3, +2, -1
-
LiCl, BeCl2,
BCl3, CCl4 then NCl3, Cl2O
(OCl2),
ClF (FCl)
-
*
C can be (+2) in CO and from -1 to + 4 in organic compounds -
a complex area in terms of oxidation state - but this
knowledge is not needed for UK ASA2 level, if interested see
Redox Reactions Part 3.
-
-
-
Reaction of
element with oxygen and the structure of the oxide:
(Gp 1) 4Li(s)
+ O2(g) ==> 2Li2O(s)
slow, fast when heated |
(Gp 2) 2Be(s)
+ O2(g) ==> 2BeO(s)
at high temperature |
(Gp 3) 4B(s)
+ 3O2(g) ==> 2B2O3(s)
at high temperature |
(Gp 4)
C(s) + O2(g)
==> CO2(g) at
high temperature |
(Gp 5)
N2(g) +
O2(g) ==> 2NO(g)
at high temperature, NO rapidly forms NO2
in air/oxygen |
(Gp 6) in ozone layer O + O2
==> O3 |
(Gp 7) Fluorine - no reaction |
(Gp 0) Neon - no reaction |
-
Reaction with oxygen
and the structure of the oxide
-
The metal Li burns in
air/oxygen to
form a giant ionic lattice oxide Li2O or (Li+)2O2-
-
Beryllium forms a giant lattice oxide (BeO has an intermediate
ionic-covalent structure).
-
Boron forms a giant covalent lattice of B2O3.
-
Carbon forms simple covalent molecular CO2 gas
(or CO).
-
Nitrogen forms a
variety of simple molecular covalent gaseous oxides up to N2O5.
-
Fluorine can
form F2O gas.
-
In terms of the
maximum oxidation state the observed formulae comply with +1 to
+ 5 for Groups 1-5, for fluorine it is -1
-
Li2O,
BeO, B2O3, CO2, N2O5,
(O2), F2O
-
The overall bonding pattern,
from left to right is giant ionic lattice => giant covalent
lattice => small covalent molecules.
-
The change in bonding
character from ionic to covalent in the oxide, follows the
decreasing difference in electronegativity between that of the
period 2 element and oxygen.
-
-
-
Reaction of the oxides with water, acids and alkalis
(Gp 1) Li2O(s)
+ H2O(l) ==> 2LiOH(aq)
pH 13-14
strong base |
(Gp 2) BeO no reaction,
but amphoteric in nature |
(Gp 3)
B2O3 no reaction, but weakly
acidic |
(Gp 4)
CO2(aq)
+ 2H2O(l) <=>
H3O+(aq) + HCO3-(aq)
~pH 5 weak acid |
(Gp 5) N2O5(s)
+ H2O(l) ==> 2HNO3(aq)
pH 1 strong
acid |
(Gp 6) oxygen has no reaction
with water |
(Gp 7) Cl2O(g)
+ H2O(l) ==> 2HClO(aq)
weak acid pH
~3 weak acid
Cl2O7(g)
+ H2O(l) ==> 2HClO4(aq)
pH1 strong
acid |
(Gp 0) argon - no oxide |
(Gp 1) 2Li(s)
+ Cl2(g) ==> 2LiCl(s) |
(Gp 2) Be(s)
+ Cl2(g) ==> BeCl2(s) |
(Gp 3) 2B(s) +
3Cl2(g) ==> 2BCl3(l) needs high
temperature |
(Gp 4) carbon has no reaction
with chlorine |
(Gp 5) nitrogen has no reaction
with chlorine |
(Gp 6) oxygen has no reaction
with chlorine |
(Gp 7) Cl2(g) + F2(g)
==> 2ClF(g) |
(Gp 0) neon has no reaction with
chlorine |
(Gp 1) LiCl(s)
+ aq ==> Li+(aq) + Cl-(aq)
just
dissolves, neutral ~pH 7 |
(Gp 2) BeCl2(s)
+ 2H2O(l)
<=>
Be(OH)2(s) + 2HCl(aq)
hydrolysis
giving an acid solution |
(Gp 3) BCl3(l)
+ 3H2O(l) ==> B(OH)3(aq)*
+ 3HCl(aq)
hydrolysis
giving an acid solution |
(Gp 4) CCl4 no
reaction with water |
(Gp 5) NCl3(l)
+ 2H2O(l) ==> HNO2(aq) + 3HCl(aq)
hydrolysis
giving an acid solution |
(Gp 6)
Cl2O(g)
+ H2O(l) ==> 2HClO(aq)
hydrolysis
giving an acid solution |
(Gp 7) ClF + H2O ==>
acidic solution ??? |
(Gp 0) neon has no chloride |
(Gp 1) 2Li(s) +
2H2O(l) ==> 2LiOH(aq) +
H2(g) |
(Gp 2)
beryllium has no reaction with cold water |
(Gp 3)
boron has no reaction with water |
(Gp 4) C(s) +
H2O(g) ==> CO(g) + H2(g)
at high temperature |
(Gp 5)
nitrogen has no reaction with water |
(Gp 6)
oxygen has no reaction with water |
(Gp 7)
2F2(g) +
2H2O(l)
==> 4HF(aq) + O2(g) |
(Gp 0) argon has no reaction with water |
-
The reaction of the
element with water
-
The reactive metal Li
gives the hydroxide and hydrogen.
-
Beryllium and boron have no reaction
with water.
-
Carbon
reacts at high temperature.
-
Nitrogen and oxygen have no reaction
with water.
-
Fluorine reacts
violently forming oxygen and hydrogen fluoride.
-
The 'limited' pattern
for period 2 (or any other period), is to have reactive metals
on the left forming an alkaline solution of a hydroxide and hydrogen and non-metals on the
right forming acid solutions IF they react with water (only
fluorine).
-
-
-
The hydrides MHx
-
For hydrides the difference
in electronegativity works both ways!
-
From left to right across
the period you change from an ionic lithium hydride crystal lattice e.g.
-
Li+H- to small non-polar molecule covalent
hydrides (methane CH4)
-
and then a polar weakly basic covalent
hydride molecule (ammonia NH3)
-
and finally a quite acidic
polar covalent molecule (hydrogen fluoride HF).
-
The formulae follow a simple
period pattern of rising and falling valency combinations.
-
On reaction with water, the
ionic metal hydrides at the start of the period give an alkaline
solution
-
In the middle are neutral
hydrides like methane which in contact with water do not change the pH.
-
Then you get weak base ==>
moderately strongly acidic hydrides when they dissolve in water e.g.
-
So things are a bit
complicated with hydrides on period 2 and not the greatest of patterns!
-
-
-
Radii of isoelectronic
ions
-
Isoelectronic means species having the same total
number of electrons.
-
The table below considers
the isoelectronic anions associated with Periods 2 (and the table
continues with Period 3 cations).
-
isoelectronic system |
Group 4/14 |
Group 5/15 |
Group 6/16 |
Group 7/17 |
(Group 0/18) |
Group 1 |
Group 2 |
Group 3/13 |
Period |
Period 2 |
Period 3 |
[Ne]
10e 1s22s22p6 |
C4- |
N3- |
O2- |
F- |
(Ne) |
Na+ |
Mg2+ |
Al3+ |
total nuclear charge |
+6 |
+7 |
+8 |
+9 |
(+10) |
+11 |
+12 |
+13 |
radius
in
picometre (pm) |
260 |
171 |
140 |
136 |
(38-112*) |
95 |
65 |
50 |
name of ion |
carbide |
nitride |
oxide |
fluoride |
(neon) |
sodium |
magnesium |
aluminium |
-
Excluding the noble gases
themselves, there is a clear pattern of decreasing ionic radius with
increase in nuclear charge (+ atomic/proton number) for the two
isoelectronic series tabulated above.
-
From left to right the
proton/electron ratio is steadily increasing so that the electrons are
experiencing an increasingly greater attractive force of the nucleus for
the same number of electrons,
hence the steady decrease in radii for an isoelectronic series.
-
* all sorts of values
are quoted for noble gas radii e.g. atomic, covalent and ionic, but most
don't fit in the pattern above which is quite clear for all the cations and
anions listed.
-
More isoelectronic radii are
at the end of the Period 3 survey
pages or the end of the Period 4 survey
pages.
WHAT NEXT?
See also
4.1 Period 2 Survey of the
individual elements,
4.2
Period
2 element trends and explanations of physical properties,
5.1
Period 3 survey of elements,
5.2 Period 3 element trends
& explanations of physical properties,
Period 3 element trends in bonding, structure, oxidation
state, formulae & reactions, 6.1 Survey of
Period 4 elements, 6.2 Period 4 element trends in physical properties, 6.3
Period 4 element trends in bonding, formulae and
oxidation state and
6.4
Important element trends down a Group
INORGANIC Part 4
Period 2 survey sub-index : 4.1 Period 2 Survey of the
individual elements : 3. lithium :
4. Beryllium
:
5. Boron :
6. Carbon :
7. Nitrogen
:
8. Oxygen :
9. Fluorine
:
10. Neon * 4.2
Period
2 element trends and explanations of physical properties * 4.3 Period 2 element trends in bonding,
structure, oxidation state, formulae & reactions
Advanced
Level Inorganic Chemistry Periodic Table Index *
Part 1
Periodic Table history
* Part 2
Electron configurations, spectroscopy,
hydrogen spectrum,
ionisation energies *
Part 3
Period 1 survey H to He *
Part 4
Period 2 survey Li to Ne * Part
5 Period 3 survey Na to Ar *
Part 6
Period 4 survey K to Kr and important trends
down a group *
Part 7
s-block Groups 1/2 Alkali Metals/Alkaline Earth Metals *
Part 8
p-block Groups 3/13 to 0/18 *
Part 9
Group 7/17 The Halogens *
Part 10
3d block elements & Transition Metal Series
*
Part 11
Group & Series data & periodicity plots
TOP OF PAGE
|
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Website content © Dr
Phil Brown 2000+. All copyrights reserved on revision notes, images,
quizzes, worksheets etc. Copying of website material is NOT
permitted. Exam revision summaries & references to science course specifications
are unofficial. |
|