Atomic number 50

Tin

Sn
+ phase
− phase

Shells Orbitals 4d 5s 5p

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50 electrons in 5 shells: 2, 8, 18, 18, 4.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Post-transition metal
Period: 5
Group: 14
Block: p
Standard atomic weight: 118.71(1) Da
Electron configuration: [Kr] 4d¹⁰ 5s² 5p²
Phase at 25 °C: solid
Melting point: 231.93 °C
Boiling point: 2602 °C
Density: 7.287 g/cm³
Electronegativity (Pauling): 1.96
Discovered: Known to the ancients

Neighbours in the table

In Sb

A bar of tin bent in the hands gives out a sound, the tin cry, which Los Alamos attributes to crystals breaking in a highly crystalline metal. Held below 13.2 °C, it slowly turns from silver-white metal to grey powder. Their atoms are arranged differently: white tin, tetragonal, is malleable and stable above that temperature; grey tin, cubic, is brittle.

The rot spreads outward from wherever it begins, and the grey tin formed first catalyses the rest. An object left in the cold can therefore disintegrate, a failure called tin pest. Small additions of antimony or bismuth prevent it, Los Alamos says.

Tin itself stacks 50 electrons 2, 8, 18, 18 and 4 into shells, short form [Kr] 4d¹⁰ 5s² 5p². The filled 4d subshell counts as core; the four valence electrons are 5s and 5p. A main-group atom loses the electrons added last, so the 5p pair goes first and Sn²⁺ keeps its 5s pair. OpenStax calls it the inert pair effect, an ion two oxidation states below the group’s.

Tin(IV) turns up in covalent compounds: tin(II) chloride is an ionic solid, tin(IV) chloride a covalent liquid, and the tin-to-Cl₂ ratio, 1:1 or 1:2, decides which forms. Heated in air, tin burns to SnO₂ where lead stops at PbO, the inert pair being strongest in a group’s heaviest member.

Where it is found

Tin is scarce in rock: 2.3 milligrams in a kilogram of crust on PubChem’s record. Both Los Alamos and OpenStax name cassiterite, the oxide SnO₂, as the chief ore. That oxide is why the ancient world had tin: hot campfire coals reduce it readily, OpenStax notes. Jefferson Lab’s text in the same record puts human use at 5,500 years or more.

The US Geological Survey estimates world mine output at 300,000 metric tons of contained tin for 2024: China 69,000, Indonesia 50,000, Burma 34,000 and Peru 31,000. Jefferson Lab says tin is chiefly mined in Malaysia, and Los Alamos counts Malaya among the main suppliers; Malaysia’s 2024 output was 3,000 tons. Reserves exceed 4.2 million tons.

No American mine has produced tin since 1993 and no smelter has run since 1989; imports covered 73 per cent of 2024 use. Extracting the metal is a chemical reduction, which OpenStax says costs far less than electrolysis. Roasting drives off arsenic and sulfur as volatile oxides, and hydrochloric acid washes out other metals’ oxides. Carbon heated with the ore above 1000 °C then takes the oxygen away as carbon monoxide.

Why it matters

The US Geological Survey splits 2024 American use into tinplate 23 per cent, chemicals 22, solder 11 and alloys 10, with Babbitt, bronze, brass and tinning taking 6. Tinplate works because tin reacts slowly with air, and OpenStax gives passivation, a protective coating formed in air, as part of the reason.

Bronze came first among alloys: Jefferson Lab’s text in PubChem’s copper record calls it the first alloy people made, copper strengthened with up to 25 per cent tin. The same text dates that trick to about 5,000 years ago. Pewter, bell metal, Babbitt metal and phosphor bronze follow on Los Alamos’s list. Galinstan, gallium with indium and tin, now fills thermometers that once held mercury.

A crystalline tin-niobium alloy superconducts at very low temperatures. Los Alamos describes magnets wound from its wire that weigh a few pounds and, started from a small battery, match a 100-ton electromagnet. A superconductor loses no energy because it carries current with no resistance, OpenStax explains. NbTi and Nb₃Sn, the tin alloy, alike need cooling below about −250 °C, which means liquid helium. Tin-117m, half-life 14 days, images bone and treats the pain of cancer that has spread to bone. IUPAC’s note in PubChem’s record says its decay harms healthy tissue less than other treatments.

Properties

Properties of tin Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	50
Standard atomic weight	118.71(1) Da	Da	IUPAC/CIAAW 2024
Melting point	231.93 °C	°C	Los Alamos: 231.93 °C
Boiling point	2602 °C	°C	Los Alamos: 2602 °C
Density	7.287 g/cm³	g/cm³
Electronegativity (Pauling)	1.96
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p²
Phase at 25 °C	solid

Safety

Tin as a can lining or a bar of the metal is harmless in everyday use; 72.9 per cent of the reports on PubChem’s record find no GHS hazard. The hazards the sheets list belong to dust in workplaces: irritated eyes and airways, stannosis, a benign dust disease of the lung, and powder that may ignite. Japan’s classification on the same record goes further than Europe’s and marks the metal Danger for lung damage on repeated exposure. The PubChem Laboratory Chemical Safety Summary and the NIOSH pocket guide are the sheets for anyone working with the powder.

Questions

Is a tin can made of tin?

The can itself is steel. Jefferson Lab's text in PubChem's record describes a thin coat of tin on both faces of the sheet, put there to stop the steel rusting. Tinplate was still 23 per cent of American tin use in 2024 by the US Geological Survey's count. The same survey lists aluminium, glass, paper, plastic and tin-free steel as substitutes, and PubChem says plastic and aluminium containers have largely taken the can's place.

Why is the symbol for tin Sn?

Sn abbreviates stannum. The CIAAW history in PubChem's record says the Latin word named alloys containing lead; Los Alamos gives stannum simply as the Latin for tin. The English name descends from the Anglo-Saxon tin, whose origin nobody knows. CIAAW calls the element known in prehistoric times.

Is tin toxic?

Not in the forms most people meet. Los Alamos calls the small amount of tin in canned food quite harmless. What the safety sheets watch is dust and powder in workplaces, which irritate the eyes and airways. The trialkyl and triaryl tin compounds used as biocides are a separate class; Los Alamos treats them apart from the metal and calls for careful handling.

How is tin used to make window glass?

In the Pilkington process, as Jefferson Lab's text in PubChem's record describes it, molten glass is poured onto a bath of molten tin. The glass floats there and cools, and the sheet comes off with two flat, parallel faces; the same text says this is how most window glass is now made. Los Alamos adds a second use on glass: tin salts sprayed onto the surface leave an electrically conductive coating, used for panel lighting and frost-free windshields.

Why is tin used in solder?

It melts low: 231.93 °C on PubChem's record, against more than 1000 °C for the transition metals, a gap OpenStax traces to weaker metallic bonding. Jefferson Lab's text in PubChem's lead record describes solder as nearly half lead and half tin, joining electrical components and pipes. The US Geological Survey reports tin taking lead's place in solder for drinking-water systems and electronics moving to lead-free solders; solder was 11 per cent of American tin use in 2024.

Tin