Silver – facts and properties
- Symbol
- Ag
- Atomic number
- 47
- Atomic mass
- 107.868 u
- Period
- 5
- Group
- 11
- Category
- transition metal
- Electron configuration
- [Kr] 4d¹⁰ 5s¹
- Electronegativity
- 1.93
- Atomic radius
- 165 pm
- Valence electrons
- 11
- State at standard conditions
- solid
- Melting point
- 961.78 °C
- Boiling point
- 2162 °C
- Density
- 10.501 g/cm³
- Discovered
- known since antiquity
Silver is a soft, shiny white precious metal with atomic number 47. It has been known since antiquity and was long used as money and jewellery. No other metal conducts electricity and heat better, so silver is found in solar cells, switches and many other components. Its symbol Ag comes from the Latin word argentum. In air silver turns dark, because sulfur compounds form a layer of silver sulfide.
Position in the periodic table
Occurrence and extraction
Silver occurs native, as the pure metal, but mostly in ores. The most important silver mineral is silver glance (acanthite, formerly called argentite), a sulfide with the formula Ag₂S. Most silver today is a by-product of mining lead, zinc, copper and gold. Major producers are Mexico, China and Peru. More silver comes from recycling jewellery, cutlery, electronics and old photographic materials.
Because silver has been mined for thousands of years, there is no particular year of discovery. It was smelted from lead ores as early as antiquity, and it was the basis of great coinages, for example in ancient Athens and the Roman Empire. Silver is far rarer than copper, but clearly more common than gold and platinum.
Properties and reactions
Silver is in period 5 and group 11, between palladium and cadmium and below copper. Its electron configuration is [Kr] 4d¹⁰ 5s¹ and its electronegativity is 1.93. The metal has a density of 10.501 g/cm³, melts at 961.78 °C and boils at 2162 °C. It is soft, very ductile and can be rolled into wafer-thin foil.
Pure silver has the highest electrical and thermal conductivity of all metals. It also reflects visible light particularly well, which makes it the classic material for mirrors.
Silver is a precious metal, but it reacts with sulfur compounds. Even traces of hydrogen sulfide in the air, or sulfur from eggs, onions and rubber, form a dark layer of silver sulfide: tarnish. The metal does not react with oxygen at room temperature. In compounds it almost always has the oxidation number plus one. Nitric acid dissolves it, forming silver nitrate.
Silver halides such as silver chloride and silver bromide are sensitive to light: light deposits metallic silver from them. Silver chloride is barely soluble in water and forms a white precipitate, which is used to detect chloride ions.
Uses in everyday life and technology
Silver is used for jewellery, cutlery and coins. Pure silver is too soft for this, so it is usually alloyed with copper. Sterling silver contains 925 parts silver in a thousand parts of metal, the rest mostly copper. Silver bars and coins are also traded as investments.
The largest amounts go into technology. Because of its conductivity, silver is found in electrical contacts, conductive pastes and the fine lines on solar cells. Mirrors and reflectors use its high reflectivity.
Photography relied for a long time on silver halides. On film and photographic paper, light alters the silver bromide, and developing turns this into the visible image. Digital photography has largely replaced this use.
Silver ions kill bacteria. This is used in wound dressings, some textiles and water filters. How strong and useful the effect is in daily life depends on the product. If silver ions reach waters through waste water, they harm small organisms there; the metal itself is of little harm to people.
Molecules containing this element
- Silver nitrate AgNO3
- Silver behenate C21H43COOAg
Quick question
Which metal reacts more vigorously with water?
FAQ
Why does silver tarnish?
Silver reacts with sulfur-containing substances in the air, mainly hydrogen sulfide. A dark layer of silver sulfide, Ag₂S, forms on the surface. Oxygen does not attack the metal itself. The layer can be polished off or removed chemically.
What is sterling silver?
Sterling silver is an alloy of silver and copper with 925 parts silver in a thousand. The copper makes the silver harder and more durable. It is often marked with the stamp 925.
Why does silver conduct electricity so well?
The electron configuration [Kr] 4d¹⁰ 5s¹ shows a single outer electron per atom, which can move almost freely in the metal. Together with the regular metal lattice, this gives very low electrical resistance. Copper and gold are built similarly; in silver the electrons are scattered least by the lattice, which puts it narrowly ahead.