5.3: Group 12 Metals

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Sulfide ores of zinc, Zn, cadmium, and mercury, Hg, of Group 12 metals (Table \(\PageIndex{3}\)) serve as raw materials in metallurgy. These metals are located immediately after the transition metals in the periodic table but they do not behave like transition metals because their d orbitals are filled, and zinc and cadmium exhibit properties intermediate between hard and soft reactivities of magnesium. Mercury is soft and a liquid and it tends to bond to phosphorus or sulfur ligands. Mercury forms monovalent and divalent compounds but monovalent mercury is actually Hg²⁺. This is a cationic species which has a Hg-Hg bond, and mercury further catenates to give, for example, Hg₄(AsF₆)₂.

Table \(\PageIndex{3}\) Properties of group 12 metals
	mp (°C)	bp (°C)	d(25 °C) (g cm^-3)	E⁰ (V) M²⁺+2e^-	I first	(kJ mol ^-1) second	third
Zn	420	907	7.14	-0.76	906	1733	3831
Cd	321	767	8.65	-0.40	877	1631	3644
Hg	-38.8	357	13.5	0.85	1007	1809	3300

Cadmium and mercury are poisonous, especially organic cadmium and organic ercury compounds are deadly poisons and should be handled carefully.