Oxidation states of nickel and reactions with it

Physical and chemical properties of nickel

[Deposit Photos]

Nick­el is a chem­i­cal­ly low-ac­tive met­al, with a sil­very-white col­or. The el­e­ment has the sym­bol Ni and is lo­cat­ed in the tenth group of the fourth pe­ri­od in the pe­ri­od­ic sys­tem.

The name of this el­e­ment has an in­ter­est­ing ori­gin: Nico­laus, which nick­el was named af­ter, was the name of an evil spir­it in Ger­man mythol­o­gy, a mis­chievous, two-faced char­ac­ter. This is be­cause the ore that nick­el is ex­tract­ed from looks very sim­i­lar to cop­per, but by its chem­i­cal com­po­si­tion is nick­el ar­senide (red nick­el pyrite), which re­leas­es poi­sonous ar­senic gas­es when melt­ed. At­tempts to ex­tract cop­per were un­suc­cess­ful, but in 1751 the Swedish min­er­al­o­gist Cron­st­edt ex­tract­ed a green ox­ide, and by re­duc­ing it ob­tained a met­al which was sub­se­quent­ly named nick­el.

Nick­el in na­ture

The main nick­el ores are:

  • nick­e­line (red nick­el pyrite, cop­per-nick­el) NiAs;
  • miller­tie (yel­low nick­el pyrite) NiS;
  • pent­la­dite (Fe,Ni)₉S₈;
  • ma­gen­tic pyrite (Fe, Ni, Cu)S;
  • ar­senic-nick­el glance (gers­dorf­fite) Ni­AsS.
Pentlandite in pyrrhotite [Flickr, Creative commons by James St. John is licensed under CC BY 2.0]

Ap­pli­ca­tion of nick­el

Al­though this el­e­ment has a low chem­i­cal ac­tiv­i­ty, it has found wide ap­pli­ca­tion in in­dus­try, for ex­am­ple nick­el is used to coat oth­er met­als to pro­tect them from cor­ro­sion. Very fine met­al plates can also be made from nick­el, which are used in elec­tron­ics, for ex­am­ple in bat­ter­ies.

Nick­el al­loys are also used in pros­the­ses and den­tal braces.

[Deposit Photos]

Phys­i­cal prop­er­ties of nick­el

Nick­el is a met­al of a sil­very-white col­or, which does not grow dull. In air, it be­comes cov­ered with an ox­ide film.

In it­self nick­el is very hard, but at the same time it is quite mal­leable and duc­tile.

Melt­ing tem­per­a­ture 1455 °C, boil­ing tem­per­a­ture around 2900 °C, den­si­ty 8.90 kg/dm³. Nick­el is fer­ro­mag­net­ic, with a Curie point of around 358 °C.

Chem­i­cal prop­er­ties of nick­el

Nick­el in com­pounds can have the fol­low­ing ox­i­da­tion states: +1, +2, +3 and +4. Com­pounds in which nick­el has an ox­i­da­tion state of +4 are very rare and un­sta­ble.

When heat­ed above 800°C it re­acts with oxy­gen, form­ing nick­el ox­ide:

2Ni + O₂ → 2NiO

Bunsenite — the mineralogical form of NiO [Wikimedia]

Nick­el pow­der ig­nites spon­ta­neous­ly in air and nick­el ox­ides form:

5Ni + 3O₂ → 3NiO + Ni₂O₃

It in­ter­acts with car­bon monox­ide, form­ing the poi­sonous gas car­bonyl:

Ni + 4СO → Ni(СO)₄

It in­ter­acts with ni­tro­gen at a high tem­per­a­ture, form­ing nick­el ni­tride:

Ni + N₂ = Ni₃N₂ ?

With sul­fur the re­ac­tion takes place exother­mi­cal­ly:

Ni + S = NiS

When heat­ed, it forms com­pounds of a non-sto­i­chio­met­ric com­po­si­tion with car­bon, boron, sil­i­con and phos­pho­rus, for ex­am­ple:

3Ni + C = Ni₃C,

2Ni + B = Ni₂B,

Ni + Si = NiSi,

3Ni + P = Ni₃P.

The met­al re­acts with halo­gens, form­ing halo­genides:

Ni + Cl₂ = NiCl₂.

Nick­el can ab­sorb hy­dro­gen, form­ing sol­id so­lu­tions of hy­dro­gen in nick­el.

Metal­lic nick­el re­acts with ni­tric acid:

3Ni + 8H­NO₃ = 3Ni(NO₃)₂ + 2NO + 4H₂O

When heat­ed it re­acts with con­cen­trat­ed ni­tric and sul­fu­ric acids:

Ni + 2H₂­SO₄ = NiSO₄ + SO₂ + 2H₂O,

Ni + 4H­NO₃ = Ni(NO₃)₂ + 2NO₂ + 2H₂O.

Anhydrous nickel(II) sulfate [Wikimedia]

With di­lut­ed so­lu­tions of hy­drochlo­ric and sul­fu­ric acid,

Ni + 2HCl = NiCl₂ + H₂,

Ni + H₂­SO₄ = NiSO₄ + H₂;

Nick­el forces met­als out of their salt so­lu­tions which are lo­cat­ed to the right of it in the elec­tro­chem­i­cal se­ries:

Ni + Cu­SO₄ = NiSO₄ + Cu.

Nick­el does not in­ter­act with wa­ter, al­ka­lis or flu­o­rine even when heat­ed.

Here you’ll find amaz­ing ex­per­i­ments for learn­ing prop­er­ties of dif­fer­ent met­als.

Re­ac­tion for de­tect­ing nick­el ions

To con­duct the qual­i­ta­tive re­ac­tion for nick­el, Chugaev’s reagent (dimethyl gly­oxime) is used. If Chugaev’s reagent is added to an am­mo­ni­um so­lu­tion of nick­el salt, a sed­i­ment of a bright crim­son col­or forms. With this re­ac­tion, ions of nick­el can be de­tect­ed. Nick­el can even be de­tect­ed if there is a low con­tent of nick­el ions in the so­lu­tion, in any case the so­lu­tion turns crim­son when the reagent is added.