Zinc
Zinc, in commerce also spelter, is a chemical element with symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. In some respects zinc is chemically similar to magnesium:its ion is of similar size and its only common oxidation state is +2.
Identity
- Atomic mass
- 65.382 u
- Category
- Transition metals
- Group
- 12
- Period
- 4
- Block
- d
- Oxidation States
- +2
- Phase (25 °C)
- Solid
- Appearance
- silver-gray
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10
- Short configuration
- [Ar] 3d10 4s2
- Electrons per shell
- 2, 8, 18, 2
- Electronegativity (Pauling)
- 1.65
- Electron affinity
- -58 kJ/mol
- 1st ionization energy
- 906 kJ/mol
- Ionization energies
- 906 · 1733 · 3833 · 5731 · 7970… kJ/mol
Physical properties
- Melting point
- 419.5 °C (693 K)
- Boiling point
- 906.9 °C (1180 K)
- Density
- 7.14 g/cm³
- Molar heat capacity
- 25.5 J/(mol·K)
Chemical behavior of zinc
Zinc has an electronic configuration [Ar] 3d¹⁰ 4s², with the 3d subshell completely filled. When reacting, it exclusively loses its two external 4s electrons to form a diamagnetic Zn²⁺ cation with configuration [Ar] 3d¹⁰. Unlike typical transition metals, it does not present variable valences or coloured complexes, behaving chemically in a manner similar to magnesium. It is an amphoteric metal of moderate reactivity: it oxidises superficially in humid air forming a protective film of basic carbonate, and dissolves easily in both strong acids and bases, releasing hydrogen.
Reactivity
Zn + 2 HCl → ZnCl₂ + H₂
It reacts with non-oxidising acids such as dilute hydrochloric acid, releasing hydrogen gas bubbles in a classic laboratory method for generating H₂.
2 Zn + O₂ → 2 ZnO
When heated in air above its boiling point, it burns with a bright white-green flame, producing white zinc oxide flakes ('philosopher's wool').
Zn + 2 NaOH + 2 H₂O → Na₂[Zn(OH)₄] + H₂
Due to its amphoteric character it reacts in concentrated sodium hydroxide solutions, dissolving as zincate ion ([Zn(OH)₄]²⁻) and releasing hydrogen.
Zn + CuSO₄ → ZnSO₄ + Cu
Due to its more negative reduction potential, it spontaneously displaces copper from copper(II) sulfate solutions, decolourising the blue solution and depositing metallic copper.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Zinc oxide | ZnO | White powder; mineral UVA/UVB sunscreen in cosmetics, rubber vulcanisation and antiseptic dermatological ointments |
| Zinc heptahydrate sulfate | ZnSO₄·7H₂O | White vitriol; agricultural and animal supplementation, leather tanning and rayon manufacturing |
| Zinc chloride | ZnCl₂ | Soft solder deoxidiser due to its ability to dissolve metallic oxides, wood preservation and flame retardant |
| Zinc sulfide | ZnS | Luminescent phosphor in X-ray screens, cathode tubes, photoluminescent paints and infrared windows |
Electron shell distribution
View in the atom builderIsotopes
Natural zinc is a mixture of five stable isotopes: zinc-64 (⁶⁴Zn, 49.17% with 34 neutrons), zinc-66 (⁶⁶Zn, 27.73%), zinc-68 (⁶⁸Zn, 18.45%), zinc-67 (⁶⁷Zn, 4.11%) and zinc-70 (⁷⁰Zn, 0.62%). More than two dozen artificial radioactive isotopes have been characterised; zinc-65 (⁶⁵Zn, with a half-life of 244 days and gamma emission of 1.115 MeV) is commonly used in biochemical and environmental science research as a tracer of heavy metal flow in soils and plants.
Occurrence and production
It is the 22nd most abundant element in the lithosphere (about 70-75 ppm). It never appears in native state. Its main commercial ore is zinc blende or sphalerite (zinc sulfide, ZnS), frequently associated with lead and copper sulphides; other secondary sources are smithsonite (zinc carbonate) and hemimorphite (zinc silicate). The world's main producers are China, Peru and Australia. Metallurgical extraction is based on roasting the sulphide to oxide, followed by acid leaching and electrowinning (hydrometallurgical method), or by carbothermic reduction in pyrometallurgical furnaces.
History and origin of the name
Although its minerals were already used in ancient Greece and Rome to produce brass by melting together with copper, the isolation of pure metal was first dominated in India in the 12th century and in China. In Europe, Andreas Sigismund Marggraf rediscovered the scientific procedure for distilling metallic zinc in 1746, heating calamine with carbon in closed retorts. The term 'zinc' probably derives from the German 'Zinke' (point or prong), referring to the sharp, toothed shape of the solidified metal crystals.
Applications and relevance of zinc
Uses of the element
More than 50% of the world's zinc production is dedicated to galvanising profiles, sheets and steel fasteners to protect them against atmospheric corrosion. It is used in pressure-injected die-cast alloys (Zamak) for mechanical and automotive components, in brass (alloy with copper), as sacrificial anodes to protect ship hulls and submerged installations, and as the anode of dry cells and zinc-air batteries.
Uses of its compounds
Zinc oxide is a key ingredient in rubber tyre vulcanisation, dermatological sunscreen and ceramics. Zinc sulfate is used to correct micronutrient deficiencies in agricultural soils; zinc chloride as welding flux and bactericide; and doped zinc sulfide in luminous pigments.
Health, safety and environment
Biological role
It is an essential trace element for all living things, ranking second in abundance in the body after iron. It is part of more than 300 essential enzymes, including carbonic anhydrase, alkaline phosphatase and RNA polymerases. It is indispensable for the integrity of the immune system, DNA synthesis, tissue healing and the protein structural 'zinc fingers' that regulate gene expression.
Safety
Solid metal and galvanised parts do not represent toxicity risk by contact. However, inhalation of fresh zinc oxide vapours generated when soldering galvanised parts causes acute 'soldier's fever' syndrome. Massive ingestion of soluble zinc salts causes intense vomiting, abdominal cramps and interferes with copper absorption.
Environment
Although it is indispensable for plant life in microdoses, high concentrations of dissolved zinc in rivers and streams from mining effluents or urban runoff are toxic to fish and aquatic plants, stunting their growth and affecting photosynthesis.
Frequently asked questions about Zinc
How does zinc protect steel when the protective layer is scratched?
Zinc protects steel in two ways. First, it forms a barrier that makes it difficult for iron to contact water and oxygen. In addition, if the layer is scratched, zinc corrodes before the iron and helps prevent the exposed steel from oxidising. That is why it is used to coat roofs, fences, screws and other metal parts that must resist the elements.
Why does zinc oxide block solar radiation in dermatological creams without decomposing?
Unlike conventional chemical filters that absorb solar photons and end up degrading photochemically after a few hours, zinc oxide acts as an inorganic physical filter. Its mineral particles reflect, refract and scatter complete ultraviolet radiation (both UVA and UVB). It is a photostable and inert compound that does not penetrate the bloodstream, does not cause skin irritation and does not produce harmful free radicals in the skin.
Why can taking too much zinc cause copper deficiency?
Consuming large amounts of zinc for a long time can make it difficult for the intestine to absorb copper from food. If this situation persists, the body can run out of enough copper to make red blood cells and maintain the nervous system in good condition. That is why zinc supplements should be used in recommended amounts and not taken in high doses for extended periods without medical guidance.
Why do hearing aids use zinc-air button batteries?
Hearing aid batteries use a very ingenious technology: they use oxygen from the surrounding air as one of the reactants to generate electricity. When the protective seal is removed from the battery, air enters through some microperforations and reacts with the internal zinc powder. This saves a lot of space and allows the manufacture of ultracompact batteries with long life.
How does zinc help our cells use information from DNA?
Some proteins need zinc to adopt the correct shape and recognise specific parts of DNA. These proteins can activate or deactivate certain genes, helping cells manufacture the substances they need and regulate their function. That is why zinc is important for processes such as growth, tissue repair and the normal functioning of the immune system.
Why are zinc blocks placed on ship hulls?
Seawater oxidises steel easily. To prevent this, shipbuilders screw zinc pieces onto the submerged hull and near the propellers. As zinc is chemically more reactive than iron, it corrodes first and 'sacrifices', protecting the ship's structure intact until the pieces wear out and are replaced.
What is Zamak alloy and why is it used so much in injection moulds and automotive parts?
Zamak is the commercial acronym for a family of alloys composed mainly of zinc plus rigorous proportions of aluminium, magnesium and copper. It has a low melting point (around 400 °C), excellent liquid fluidity and minimal shrinkage when cooling. These qualities allow pressure injection moulding of parts with great geometric complexity, thin walls and millimetre mechanical tolerances, such as locks, handles, carburettors, electronic casings and metal toys, with very competitive costs.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.