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Doc Brown's Chemistry  Advanced Level Inorganic Chemistry Periodic Table Revision Notes – Transition Metals

Part 10. Transition Metals 3d–block:  10.10 Nickel Chemistry

The chemistry of nickel is dominated by the +2 oxidation state with many nickel(II) complexes known.

principal oxidation states of nickel, redox reactions of nickel, ligand substitution displacement reactions of nickel, balanced equations of nickel chemistry, formula of nickel complex ions, shapes colours of nickel complexes, formula of compounds

(c) doc b GCSE/IGCSE Periodic Table Revision Notes * (c) doc b GCSE/IGCSE Transition Metals Revision Notes

INORGANIC Part 10 3d block TRANSITION METALS sub–index: 10.1–10.2 Introduction 3d–block Transition Metals * 10.3 Scandium * 10.4 Titanium * 10.5 Vanadium * 10.6 Chromium * 10.7 Manganese * 10.8 Iron * 10.9  Cobalt * 10.10 Nickel * 10.11 Copper * 10.12 Zinc * 10.13 Other Transition Metals e.g. Ag and Pt * 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

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


10.10. Chemistry of Nickel Ni, Z=28, 1s22s22p63s23p63d84s2 

data comparison of nickel 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. 3d14s2 3d24s2 3d34s2 3d54s1 3d54s2 3d64s2 3d74s2 3d84s2 3d104s1 3d104s2
Electrode potential M(s)/M2+(aq) na –1.63V –1.18V –0.90V –1.18V –0.44V –0.28V –0.26V +0.34V –0.76V
Electrode potential M(s)/M3+(aq) –2.03V –1.21V –0.85V –0.74V –0.28V –0.04V +0.40 na na na
Electrode potential M2+(aq)/M3+(aq) na –0.37V –0.26V –0.42V +1.52V +0.77V +1.87V na na na

Extended data table for NICKEL

property of nickel/unit value for Ni
melting point Ni/oC 1455
boiling point Ni/oC 2730
density Ni/gcm–3 8.90
1st Ionisation Energy Ni/kJmol–1 737
2nd IE/kJmol–1 1753
3rd IE/kJmol–1 3393
4th IE/kJmol–1 5300
5th IE/kJmol–1 7280
atomic radius Ni/pm 125
Ni2+ ionic radius/pm 72
Relative polarising power Ni2+ ion 2.8
Ni3+ ionic radius/pm 62
Relative polarising power Ni3+ ion 4.8
oxidation states of Ni, less common/stable +2, +3
simple electron configuration of Ni 2,8,16,2
outer electrons of Ni [Ar]3d84s2
Electrode potential Ni(s)/Ni2+(aq) –0.26V
Electrode potential Ni(s)/Ni3+(aq) na
Electrode potential Ni2+(aq)/Ni3+(aq) na
Electronegativity of Ni 1.91

Advanced Inorganic Chemistry Page Index and Links

  • Uses of NICKEL

    • Nickel is a moderately hard silvery–white metal, lustrous like most transition metals and malleable and ductile.

    • Nickel is quite resistant to corrosion and not affected by water but will dissolve slowly in most strong acids.

    • Nickel has many uses from 'silver' coinage metals like cupro–nickel, which is an alloy of nickel and copper that doesn't readily corrode.

    • Along with chromium, nickel is used in stainless steels.

    • Alnico alloy (Al + Ni + Co) is used to make permanent magnets.

    • Nichrome wire (Ni + Cr) is used to make wire for windings in electric motors.

    • Nickel is a constituent of monel metal alloy used to make ships propeller shafts and chemical reactor vessels because of its strength and anti–corrosion properties.

    • Nickel is an important hydrogenation catalyst in converting unsaturated vegetable oils to saturated fats like margarine.

      • unsaturated oil + hydrogen ==> low melting solid more saturated fat

      • Along the carbon chain of the vegetable oil you get: –CH=CH– + H2 ==> –CH2–CH2

    • Solutions of nickel(II) salts or complexes are used in electroplating nickel onto other metal surfaces.

      • e.g. the complex ion salt Ni(NH4)2(SO4)2.6H2O

    • Nickel(II) oxide, NiO, is used in pigments.

  • Biological role of nickel

    • It is apparently found in human tissue, but its role is unknown.


The Chemistry of NICKEL

  • The electrode potential chart highlights the values for various oxidation states of nickel.

  • NICKEL(II) CHEMISTRY

  • In aqueous solution nickel forms the green stable hexaaqua nickel(II) ion, [Ni(H2O)6]2+(aq) from eg nickel(II) chloride solution NiCl2(aq) or nickel(II) sulphate NiSO4(aq), both of which are suitable for laboratory experiments for investigating the aqueous chemistry of the nickel(II) ion..

  • With alkalis sodium hydroxide or ammonia, nickel(II) ions produce the hydrated nickel(II) hydroxide green? precipitate. There is no further reaction with excess of NaOH, but see further down for excess NH3.

    • Ni2+(aq) + 2OH(aq) ==> Ni(OH)2(s)  (can be written as [Ni(OH)2(H2O)4])

      • a precipitation reaction

  • With alkaline aqueous sodium carbonate solutions, nickel(II) ions produces a precipitate of green ppt. of nickel(II) carbonate.

    • Ni2+(aq) + CO32–(aq) ==> NiCO3(s) 

      • Its actually a basic carbonate – a mixture of the hydroxide and carbonate, you can make the pure carbonate by using sodium hydrogencarbonate solution.

      • Ni2+(aq) + 2HCO3(aq) ==> NiCO3(s) + 4H2O(l) + CO2(g)

  • With excess aqueous ammonia the blue hexammine complex ion is formed from the hexaaquanickel(II) ion – a typical ligand substitution reaction:

  • [Ni(H2O)6]2+(aq) + 6NH3(aq) rev [Ni(NH3)6]2+(aq) + 6H2O(l)

    • [Ni(H2O)6]2+(aq) + 6NH3(aq) ==> [Ni(NH3)6]2+(aq) + 6H2O(l)

      • Kstab = {[Ni(NH3)6]2+(aq)} / {[Ni(H2O)6]2+(aq)} [NH3(aq)]6

      • Kstab = 4.8 x 107 mol–6 dm18  [lg(Kstab) = 7.7]

    • You can write equation of the ammine complex from the dissolving of nickel(II) hydroxide precipitate.

      • Ni(OH)2(s) + 6NH3(aq) rev [Ni(NH3)6]2+(aq) + 2OH(aq)

    • With lower concentrations of ammonia the pale blue complex can also have the structure [Ni(H2O)2(NH3)4]2+

    • The hexaaquanickel(II) ion also forms complexes with other amine ligands

      • e.g. the bidentate ligand 1,2–diaminoethane (H2N–CH2–CH2–NH2, often abbreviated to en from its old trivial name of ethylenediamine)

      • [Ni(H2O)6]2+(aq) + 3en(aq) ===> [Ni(en)3]2+(aq) + 6H2O(l)

        • Kstab = {[Ni(en)3]2+(aq)} / {[Ni(H2O)6]2+(aq)} {[en(aq)]3}

        • Kstab = 2.0 x 1018 mol–3 dm9 [lg(Kstab) = 18.3]

      • The complex with EDTA is also readily formed.

      • [Ni(H2O)6]2+(aq) + EDTA4–(aq) ===> [Ni(EDTA)]2–(aq) + 6H2O(l)

        • Kstab = {[Ni(EDTA)3]2–(aq)} / {[Ni(H2O)6]2+(aq)} {[EDTA4–(aq)]}

        • Kstab = 1.0 x 1019 mol–1 dm3 [lg(Kstab) = 19.0]

      • Note that Kstab for the same ion tend to increase the greater the chelating power of an individual ligand in terms of the ligand bond formed – mainly due to the increase in entropy as more particles are formed by the polydentate ligands

      • e.g. for the same nickel(II) ion Kstab(EDTA) > Kstab(en) > Kstab(NH3)

  • VIEW ppts. with OH, NH3 and CO32–, & complexes, if any, with excess reagent.

  • Other complexes of nickel

    • Nickel carbonyl, Ni(CO)4, is a neutral complex tetrahedrally shaped covalent molecule. Note (i) nickel is in a zero oxidation state and (ii) the ligand CO also acts as ligand with haemoglobin (hemoglobin) in carbon monoxide poisoning.

    • Ni2+ forms the tetrachloronickelate(II) ion, [NiCl4]2–, a tetrahedral anionic complex with the chloride ion ligand (Cl).

      • [Ni(H2O)6]2+(aq) + 4Cl(aq) ==> [NiCl4]2–(aq) + 6H2O(l)

      • Kstab = {[NiCl4]2–(aq)} / {[Ni(H2O)6]2+(aq)} [Cl(aq)]4

      • Kstab = ? mol4 dm–12  [lg(Kstab) = ?]

    • Ni2+ forms the tetracyanonickelate(II) ion, [Ni(CN)4]2–, a square planar anionic complex with the cyanide ion (CN).

      • [Ni(H2O)6]2+(aq) + 4CN(aq) ==> [NiCN4]2–(aq) + 6H2O(l)

      • Kstab = {[NiCN4]2–(aq)} / {[Ni(H2O)6]2+(aq)} [CN(aq)]4

      • Kstab = 2 x 1031 mol4 dm–12  [lg(Kstab) = 31.3]

    • Its likely that the more bulky chloride ion (radius Cl > C) 'forces' the formation of the tetrahedral shape rather than a square planar shaped complex.

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


Scandium * Titanium * Vanadium * Chromium * Manganese * Iron * Cobalt * Nickel * Copper * Zinc * Silver & Platinum


keywords redox reactions ligand substitution displacement balanced equations formula complex ions complexes ligand exchange reactions redox reactions ligands colours oxidation states: nickel ions Ni(0) Ni2+ Ni(+2) Ni(II) NiCl2 NiSO4 Ni2+ + 2OH– ==> Ni(OH)2 Ni2+ + CO32– ==> NiCO3 Ni2+ + 2HCO3– ==> NiCO3 + 4H2O + CO2 [Ni(H2O)6]2+ + 6 NH3 [Ni(NH3)6]2+ + 6H2O [Ni(H2O)6]2+ + 6NH3 ==> [Ni(NH3)6]2+ + 6 H2O Kstab = {[Ni(NH3)6]2+} / {[Ni(H2O)6] 2+} [NH3]6 Ni(OH)2 + 6NH3 [Ni(NH3)6]2+ + 2OH– [Ni(H2O)6]2+ + 3en ===> [Ni(en)3]2+ + 6H2O Kstab = {[Ni (en)3]2+} / {[Ni(H2O)6]2+} {[en]3} [Ni(H2O)6]2+ + EDTA4– ===> [Ni(EDTA)]2– + 6H2O Kstab = {[Ni(EDTA)3]2–} / {[Ni (H2O)6]2+} {[EDTA4–]}[Ni(H2O)6]2+ + 4 Cl– ==> [NiCl4]2– + 6H2O Kstab = {[NiCl4]2–} / {[Ni(H2O)6]2+} [Cl–]4 [Ni(H2O)6]2+ + 4 CN– ==> [NiCN4]2– + 6H2O Kstab = {[NiCN4]2–} / {[Ni(H2O)6]2+} [CN–]4 Kstab = 2 x 1031 mol4 dm–12 [lg(Kstab) = 31.3] oxidation states of nickel, redox reactions of nickel, ligand substitution displacement reactions of nickel, balanced equations of nickel chemistry, formula of nickel complex ions, shapes colours of nickel complexes  Na2CO3 NaOH NH3


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Scandium * Titanium * Vanadium * Chromium * Manganese * 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

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