Tin: its oxidation states and reactions with it

Tin is a light met­al lo­cat­ed in the 14th group of the pe­ri­od­ic ta­ble, with the atom­ic num­ber of 50. This el­e­ment has been known to hu­man­i­ty since an­cient times and was con­sid­ered to be one of the rarest and most valu­able met­als, so items made from tin could only be af­ford­ed by the rich­est in­hab­i­tants of the Ro­man Em­pire and An­cient Greece. Spe­cial bronze was made from tin, which was used as ear­ly as the 3rd mil­len­ni­um BCE. Bronze be­came the most durable and pop­u­lar al­loy, and tin was used as one of its com­po­nents, and used for over 2,000 years.

In Latin, this met­al was called “stan­num”, which means dura­bil­i­ty and en­durance, but this name was pre­vi­ous­ly give to an al­loy of lead and sil­ver. Only in the 4th cen­tu­ry this word was giv­en to tin it­self.

This met­al is rarely en­coun­tered in na­ture, it is only the 47th most abun­dant el­e­ment in the earth’s crust and is ex­tract­ed from cas­si­terite, so-called tin-stone, which has about an 80% con­tent of this met­al.

Use in in­dus­try

As tin is non-tox­ic and a very durable met­al, it is used in al­loys with oth­er met­als, but it is main­ly used to man­u­fac­ture tin plate, which is used for cans, sol­ders in elec­tron­ics, and man­u­fac­tur­ing bronze.

Phys­i­cal prop­er­ties of tin

A white met­al with a sil­very shine

If tin is heat­ed, it cracks, which is caused by crys­tals rub­bing against each oth­er. This char­ac­ter­is­tic crack­le is heard if a piece of tin is sim­ply bent.

Tin is very mal­leable and duc­tile. In clas­si­cal con­di­tions, this el­e­ment ex­ists as “white tin” which can be mod­i­fied de­pend­ing on the tem­per­a­ture, for ex­am­ple if white tin is in the cold, it turns to gray tin, which has a struc­ture sim­i­lar to a di­a­mond. In­ci­den­tal­ly, gray tin is very brit­tle and turns to pow­der right be­fore your eyes. The term “tin pest” ex­ists in his­to­ry for this rea­son.

Peo­ple did not know about this prop­er­ty of tin, so it was used to make but­tons and mugs for sol­diers, and also oth­er use­ful items, which turned into pow­der af­ter be­ing in the cold. This put armies at a dis­ad­van­tage. For ex­am­ple, some his­to­ri­ans be­lieve that this prop­er­ty of tin re­duced the fight­ing abil­i­ty of Napoleon’s army.

Ob­tain­ing tin

The main method for ob­tain­ing tin is re­duc­ing the met­al from ore con­tain­ing tin(IV) ox­ide, with coal, alu­minum or zinc.

SnO₂ + C = Sn + CO₂.

High­ly pure tin is ob­tained by elec­tro­chem­i­cal re­fin­ing or the method of zone melt­ing.

Chem­i­cal prop­er­ties of tin

At room tem­per­a­ture, tin is quite re­sis­tant to the im­pact of air or wa­ter, as a thin ox­ide film forms on the sur­face of the met­al. In air, tin starts to ox­i­dize at a tem­per­a­ture of over 150 °C:

Sn + O₂ → SnO₂.

If tin is heat­ed, the el­e­ment will re­act with the ma­jor­i­ty of non-met­als, form­ing com­pounds with an ox­i­da­tion state of +4, which is more char­ac­ter­is­tic for this el­e­ment.

Sn + 2Cl₂ → SnCl₄

The in­ter­ac­tion of tin and con­cen­trat­ed hy­drochlo­ric acid takes place quite slow­ly:

Sn + 4HCl → H₂[SnCl₄] + H₂

With con­cen­trat­ed sul­fu­ric acid, tin re­acts very slow­ly, while it does not en­ter into a re­ac­tion with di­lut­ed sul­fu­ric acid at all.

The re­ac­tion of tin with ni­tric acid is very in­ter­est­ing, which de­pends on the con­cen­tra­tion of the so­lu­tion. The re­ac­tion takes place with the for­ma­tion of stan­nic acid, H₂S­nO₃, which is a white amor­phic pow­der.

3Sn + 4H­NO₃ + nH₂O = 3H₂S­nO₃·nH₂O + 4NO

If tin is mixed with di­lut­ed ni­tric acid, the el­e­ment will dis­play metal­lic prop­er­ties with the for­ma­tion of tin ni­trate.

4Sn + 10H­NO₃ = 4Sn(NO₃)₂ + NH₄NO₃ + 3H₂O

If tin is heat­ed, it can re­act with al­ka­lis with the re­lease of hy­dro­gen.

Sn + 2KOH + 4H₂O = K₂[Sn(OH)₆] + 2H₂

Here you’ll find amaz­ing and safe ex­per­i­ments with tin

Ox­i­da­tion states of tin

An or­di­nary ox­i­da­tion state of tin is zero.

Sn can also an ox­i­da­tion state of +2: tin(II) ox­ide SnO, tin(II) chlo­ride SnCl₂, tin(II) hy­drox­ide Sn(OH)₂.

An ox­i­da­tion state +4 is most char­ac­ter­is­tic for this el­e­ment in tin(IV) ox­ide SnO₂ and halo­genides(IV), for ex­am­ple SnCl₄, tin(IV) sul­fide SnS₂ and tin(IV) ni­tride Sn₃N₄.