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transition metal chemistry of scandium complexes oxidation state +3 redox chemical reactions physical properties advanced inorganic chemistry of scandium

Revision notes on 3d block chemistry of scandium for Advanced A Level Inorganic Chemistry

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Periodic Table 3d block Scandium chemistry - Doc Brown's Chemistry  Revising Advanced Level Inorganic Chemistry Periodic Table Revision Notes

Part 10. 3d block – Transition Metals –  

10.3 Scandium Chemistry

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GCSE Level Notes on Transition Metals (for the basics)

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Scandium is a member of the 3d–block of elements BUT why isn't scandium a true transition metal? Scandium cannot form an ion with an incomplete 3d sub–shell and is therefore not a true transition element.

Scandium's chemistry is determined solely by the formation of compounds/ions in its +3 oxidation state, but it does form many complexes, though not as many as other transition metals.

The principal oxidation state of scandium is +3 but there is little to say about redox reactions of scandium, ligand substitution displacement reactions of scandium, balanced equations of scandium chemistry, formula of scandium complex ions, shapes colours of scandium complexes, formula of compounds compared to true transition metals.

10.3. Chemistry of Scandium Sc, Z=21, 1s22s22p63s23p63d14s2

data comparison of scandium with the other members of the 3d–block and transition metals

Z and symbol 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn
property\name scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc
melting point/oC 1541 1668 1910 1857 1246 1538 1495 1455 1083 420
density/gcm–3 2.99 4.54 6.11 7.19 7.33 7.87 8.90 8.90 8.92 7.13
atomic radius/pm 161 145 132 125 124 124 125 125 128 133
M2+ ionic radius/pm na 90 88 84 80 76 74 72 69 74
M3+ ionic radius/pm 81 76 74 69 66 64 63 62 na na
common oxidation states +3 only +2,3,4 +2,3,4,5 +2,3,6 +2,3,4,6,7 +2,3,6 +2,3 +2,+3 +1,2 +2 only
outer electron config.[Ar]... 3d14s2 3d24s2 3d34s2 3d54s1 3d54s2 3d64s2 3d74s2 3d84s2 3d104s1 3d104s2
Elect. pot. M(s)/M2+(aq) na –1.63V –1.18V –0.90V –1.18V –0.44V –0.28V –0.26V +0.34V –0.76V
Elect. pot. M(s)/M3+(aq) –2.03V –1.21V –0.85V –0.74V –0.28V –0.04V +0.40 na na na
Elect. pot. M2+(aq)/M3+(aq) na –0.37V –0.26V –0.42V +1.52V +0.77V +1.87V na na na

Elect. pot. = standard electrode potential data for scandium (EØ at 298K/25oC, 101kPa/1 atm.)

na = data not applicable to scandium

Extended data table for SCANDIUM

property of scandium/unit value for Sc
melting point/oC 1541
boiling point/oC 2836
density/gcm–3 2.99
1st Ionisation Energy/kJmol–1 631
2nd IE/kJmol–1 1235
3rd IE/kJmol–1 2389
4th IE/kJmol–1 7089
5th IE/kJmol–1 8844
Sc atomic radius/pm 161
Sc3+ ionic radius/pm 81
Relative polarising power Sc3+ ion 3.7
oxidation state of Sc +3 only
simple electron configuration of Zn 2,8,9,2
outer electrons of Sc [Ar]3d14s2
Electrode potential Sc(s)/Sc3+(aq) –2.03V
Electronegativity of Sc 1.36
  • Uses of SCANDIUM

    • Scandium is a silvery–white metal and not a particularly important element but does have some uses.

    • Scandium oxide, Sc2O3, is used in electronic components.

    • Scandium iodide, ScI3, is used in high intensity light–bulbs.

    • Scandium carbide, ScC, is a hardening agent for titanium carbide, making it the second hardest substance known.

  • The colour of scandium compounds

    • Most scandium compounds and complex ions (Sc only exhibits a +3 oxidation state in them) are white or colourless.

      • The lack of scope for a variety of coloured compounds arises from the fundamental electronic configuration of the Sc3+ ion, namely [Ar]3d0, giving a completely empty 3d sub–shell.

        • ie there is no electron that can be promoted to a higher level when the 3d sub–shell is split when the central metal ion interacts with the ligands.

        • Top left shows the ground state of the scandium(III) ion, and the possible 3d orbital splitting, and clearly, no 3d electron can be promoted, so no absorption of visible light photons, all visible light transmitted, so no colour!

        • Even though scandium is a member of the 3d block of elements, this is why scandium is NOT a true member of the first transition metal series, it forms no ion with a partly filled 3d sub–shell.

        • For more details see Appendix 4. Electron configuration & complex ion colour theory


The Chemistry of SCANDIUM

Pd s block d blocks (3d block scandium) and f blocks of metallic elements p block elements
Gp1 Gp2 Gp3/13 Gp4/14 Gp5/15 Gp6/16 Gp7/17 Gp0/18
1

1H

2He
2 3Li 4Be The modern Periodic Table of Elements

ZSymbol, z = atomic or proton number

3d block of metallic elements: Scandium to Zinc focus on scandium

5B 6C 7N 8O 9F 10Ne
3 11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
4 19K 20Ca 21Sc

[Ar]3d14s2

scandium

22Ti

[Ar]3d24s2

titanium

23V

 [Ar] 3d34s2

vanadium

24Cr

[Ar] 3d54s1

chromium

25Mn

   [Ar]   3d54s2

manganese

26Fe

[Ar] 3d64s2

iron

27Co

[Ar] 3d74s2

cobalt

28Ni

[Ar] 3d84s2

nickel

29Cu

[Ar] 3d104s1

copper

30Zn

[Ar] 3d104s2

zinc

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 57,58-71 72Hf 73Ta 74W 75Re 76Os 77Ir 78Pt 79Au 80Hg 81Tl 82Pb 83Bi 84Po 85At 86Rn
7 87Fr 88Ra 89,90-103 104Rf 105Db 106Sg 107Bh 108Hs 109Mt 110Ds 111Rg 112Cn 113Nh 114Fl 115Mc 116Lv 117Ts 118Os
  *********** *********** ************ ************ ************** ********** ********** ********** ********** **********  

Summary of oxidation states of the 3d block metals (least important) Ti to Cu are true transition metals

Sc Ti V Cr Mn Fe Co Ni Cu Zn
                +1  
  (+2) (+2) (+2) +2 +2 +2 +2 +2 +2
+3 (3d0) +3 +3 +3 (+3) +3 +3 (+3) (+3)  
  +4 +4   +4     (+4)    
    +5              
      +6 (+6) (+6)        
        +7          
3d14s2 3d24s2 3d34s2 3d54s1 3d54s2 3d64s2 3d74s2 3d84s2 3d104s1 3d104s2
The outer electron configurations beyond [Ar] and the (ground state of the simple ion)

Note that when 3d block elements form ions, the 4s electrons are 'lost' first.

The oxidation state and electron configuration of scandium in the context of the 3d block of elements

electrode potential chart for scandium and scandium(III) ion complexes compounds

  • The electrode potential chart highlights the value for the one positive oxidation state of scandium.

  • Scandium is quite an electropositive metal and will dissolve in acids liberating hydrogen.

    • As you can see from the electrode potential chart above ...

    • Sc3+(aq)  +  3e-    Sc(s)   Eθ = -2.03 V

  • Scandium's chemistry is entirely based on the +3 oxidation state (Sc3+), the result of losing the outer 3d and 4s electrons.

  • So it forms a typical series of binary compounds with non–metals e.g. Sc2O3,  ScCl3 etc.

  • the hexa-aqua ion of scandium scandium(III) ion complex structureScandium dissolves in acids to form salts e.g. scandium chloride from hydrochloric acid.

    • 2Sc(s) + 6HCl(aq) ===> 2ScCl3(aq) + 3H2(g)

    • Note that the Roman numerals (III) are NOT needed in the name, since only one oxidation state is possible for scandium and you would be expected to know that.

  • With oxygen scandium forms a white basic oxide, scandium oxide Sc2O3,

    • 2Sc(s) + 3O2(g) ===> Sc2O3(s)

    • which dissolves in acids to form colourless solutions of the respective salt e.g.

    •  Sc2O3(s) + 6HCl(aq) ===> 2ScCl3(aq) + 3H2O(l)   (scandium chloride)

    •  Sc2O3(s) + 3H2SO4(aq) ===> Sc2(SO4)3(aq) + 3H2O(l)   (scandium sulfate)

    •  Sc2O3(s) + 6HNO3(aq) ===> 2Sc(NO3)3(aq) + 3H2O(l)   (scandium nitrate)

  • The scandium(III) ion, Sc3+ ion, [Sc(H2O)6)]3+ has an empty sub–shell, 3d0, which does not allow the electronic transitions which account for the colour in transition metal compounds.

  • The aqueous octahedral hexaaqua ion of scandium, [Sc(H2O)6]3+ is therefore colourless (shown as grey in the diagram!) and with no other oxidation state possible i.e. no ion with an incomplete 3d sub–shell with at least one electron, although a member of the 3d–block, scandium is NOT a true transition metal.

    • The hexa-aqua ion of scandium is a typical octahedral complex.

    • Apart from the colourless Sc3+ and Zn2+ all the other M2+ or M3+ hexaaqua ions of the 3d block are coloured.

  • With alkali, the aqueous scandium ion Sc3+ forms a white gelatinous precipitate of hydrated scandium hydroxide, Sc(OH)3,

    • diagram of the octahedral complex of scandium hydroxide scandium(III) hydroxideSc3+(aq) + 3OH(aq) ==> Sc(OH)3(s)

      • A simplified formula for the neutral hydroxide complex is [Sc(OH)3(H2O)3]0

    • Scandium hydroxide is a basic hydroxide and not amphoteric i.e. it does not dissolve in excess alkali, but scandium hydroxide readily dissolves in acids to form salts e.g. to form scandium chloride, scandium nitrate or scandium sulfate ...

    • Sc(OH)3(s) + 3HCl(aq) ===> ScCl3(aq) + 3H2O(l)

    • Sc(OH)3(s) + 3HNO3(aq) ===> Sc(NO3)3(aq) + 3H2O(l)

    • 2Sc(OH)3(s) + 3H2SO4(aq) ===> Sc2(SO4)3(aq) + 6H2O(l)

    • The chemistry of scandium is not very colourful or exciting, but scandium is not without its uses!

    • The equations are similar to those for aluminium hydroxide i.e. you can substitute Al for Sc, but not the amphoteric character of aluminium oxide/hydroxide.

  • Summary of some complexes–compounds & oxidation state of scandium compared to other 3d–block elements


keywords and phrases: Why are scandium compounds ions complexes colourless? equations for scandium reacting with acids, equations for scandium oxide reacting with strong acids, equations for scandium hydroxide reacting with acids to give scandium(III) salts, ligand substitution displacement balanced equations formula complex ions complexes ligands colours oxidation states: scandium ions Sc(0) Sc(III) Sc(+3) Sc3+ [Sc(H2O)]3+ 2Sc + 6 HCl ==> 2 ScCl3 + 3H2 2Sc + 3O2 ==> Sc2O3 + 6 HCl ==> 2ScCl3 + 3H2O  Sc2O3 + 3 H2SO4 ==> Sc2(SO4)3 + 3H2O Sc2O3 + 6 HNO3 ==> 2Sc(NO3)3 + 3H2O Sc3+ + 3OH– ==> Sc(OH)3 + 3HCl ==> ScCl3 + 3H2O Sc(OH)3 + 3HNO3 ==> Sc(NO3)3 + 3H2O 2Sc(OH)3 + 3H2SO4 ==> Sc2(SO4)3 + 6H2O [Sc(OH)3(H2O)3] oxidation states of scandium, why there are no redox reactions of scandium involving change of oxidation state for more than one ion of scandium, ligand substitution displacement reactions of scandium, balanced equations of scandium chemistry, formula of scandium complex ions, shapes colours of scandium complexes with water and hydroxide ion the position of scandium in the periodic table its reactivity with acids, quite a negative electrode potential half-cell potential

WHAT NEXT?

GCSE Level Notes on Transition Metals (for the basics)

The chemistry of Scandium * Titanium * Vanadium * Chromium * Manganese

The chemistry of Iron * Cobalt * Nickel * Copper * Zinc * Silver & Platinum

Introduction 3d–block Transition Metals * Appendix 1. Hydrated salts, acidity of hexa–aqua ions * Appendix 2. Complexes & ligands * Appendix 3. Complexes and isomerism * Appendix 4. Electron configuration & colour theory * Appendix 5. Redox equations, feasibility, Eø * Appendix 6. Catalysis * Appendix 7. Redox equations * Appendix 8. Stability Constants and entropy changes * Appendix 9. Colorimetric analysis and complex ion formula * Appendix 10 3d block – extended data * Appendix 11 Some 3d–block compounds, complexes, oxidation states & electrode potentials * Appendix 12 Hydroxide complex precipitate 'pictures', formulae and equations Some pages have a matching sub-index

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 All 11 Parts have their own sub-indexes near the top of the pages

Group numbering and the modern periodic table

The original group numbers of the periodic table ran from group 1 alkali metals to group 0 noble gases (= group 8). To account for the d block elements and their 'vertical' similarities, in the modern periodic table, groups 3 to group 0/8 are numbered 13 to 18. So, the p block elements are referred to as groups 13 to group 18 at a higher academic level, though the group 3 to 0/8 notation is still used, but usually at a lower academic level. The 3d block elements (Sc to Zn) are now considered the head (top) elements of groups 3 to 12.

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