Zinc is a bluish-silver metal, essential for life and widely used for galvanizing steel, alloys (brass), batteries, and die casting. It forms stable +2 compounds and has a filled 3d subshell.
Zinc has the ground-state configuration \([Ar]3d^{10}\,4s^2\). The common ion Zn2+ is d^{10}, so there are no d–d electronic transitions in the visible range; consequently most Zn(II) salts are colorless and diamagnetic.
Zinc provides barrier protection (a dense oxide/carbonate film) and, more importantly, cathodic (sacrificial) protection. If the coating is scratched, Zn corrodes preferentially, protecting iron:
\(\mathrm{Zn \rightarrow Zn^{2+} + 2e^-}\)
The electrons suppress \(\mathrm{Fe \rightarrow Fe^{2+}}\) at exposed steel.
Yes, zinc hydroxide is amphoteric. It dissolves in acids to give Zn2+ and in strong bases to form zincates:
Add NaOH to form a white precipitate of Zn(OH)2 that dissolves in excess base (amphoterism). With NH3, a white precipitate forms that dissolves to give the ammine complex:
\(\mathrm{[Zn(NH_3)_4]^{2+}}\)
Sulfide precipitation (acidic H2S) yields white ZnS.
Zinc dissolves in non-oxidizing acids releasing hydrogen:
\(\mathrm{Zn(s) + 2\,HCl(aq) \rightarrow ZnCl_2(aq) + H_2(g)}\)
This removes oxides/impurities (pickling) prior to galvanizing or plating. Oxidizing acids require care due to passivation or vigorous reaction.
Zinc is the anode in Zn–MnO2 alkaline cells, Zn–carbon cells, and zinc–air batteries. A simplified anode reaction in alkaline media is:
\(\mathrm{Zn + 4\,OH^- \rightarrow [Zn(OH)_4]^{2-} + 2\,e^-}\)
In zinc–air cells, O2 from air is reduced at the cathode, giving high energy density.
Brass is a Cu–Zn alloy. Zn increases strength and hardness, improves machinability, and shifts color from red (Cu) to yellow-gold (α-brass ≈ 30% Zn). Brasses are widely used in fittings, instruments, and corrosion-resistant components.
Zinc is an essential trace element in enzymes (e.g., carbonic anhydrase, alcohol dehydrogenase) and zinc-finger transcription factors that bind DNA. It stabilizes protein structure and participates in catalysis while remaining redox-inert as Zn(II).
Zinc, being more reactive, displaces Cu from Cu2+ solutions:
\(\mathrm{Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)}\)
This illustrates the relative positions in the electrochemical series (\(E^\circ_{\mathrm{Zn^{2+}/Zn}} < E^\circ_{\mathrm{Cu^{2+}/Cu}}\)).
Zinc forms a tightly adherent basic carbonate film in moist air:
\(\mathrm{2\,Zn + O_2 + 2\,CO_2 + H_2O \rightarrow 2\,ZnCO_3\cdot Zn(OH)_2}\)
This patina slows further corrosion, contributing to the long service life of galvanized steel in many environments.