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Sn

Tin

Tin (Sn) is a post-transition metal with atomic number 50 and an atomic mass of 118.71. Its electron configuration is [Kr] 4d10 5s2 5p2, which gives it 4 valence electrons.

Tin key data

Symbol Sn
Atomic number 50
Atomic mass (standard atomic weight) 118.71
Molar mass 118.71 g/mol
Protons 50
Neutrons (most abundant isotope, tin-120) 70
Electrons (neutral atom) 50
Valence electrons 4
Category Post-transition metal
Period 5
Group 14
Block p-block
Noble gas notation [Kr] 4d10 5s2 5p2
Full electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p2
Electrons per shell 2, 8, 18, 18, 4

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.

Measured properties of tin

From PubChem, the US National Institutes of Health. Public domain. The electron affinity is the measured value for tin, from Wikipedia’s electron affinity data page, in place of PubChem’s 1.2 eV.

Melting point 505.08 K (231.93 °C), 78th of 103 by melting point
Boiling point 2875 K (2601.9 °C), 44th of 93 by boiling point
Density 7.287 g/cm³, 45th of 96 by density
State at room temperature Solid
Electronegativity 1.96 (Pauling), 33rd of 95 by electronegativity
Van der Waals radius 217 pm, joint 37th of 99 by atomic radius
First ionisation energy 7.344 eV (708.6 kJ/mol), 48th of 102 by first ionisation energy
Electron affinity 1.11207 eV (107.298 kJ/mol), 21st of 57 by electron affinity
Common oxidation states +4, +2
Discovered Ancient

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Tin electron configuration

The full electron configuration of tin is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p2. With the noble-gas core collapsed it is [Kr] 4d10 5s2 5p2, and the outermost subshell is 5p2.

Bohr model of tin (Sn): a nucleus and five shells holding 2, 8, 18, 18 and 4 electrons from the inside out.
Bohr model of tin (Sn). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.
Orbital box diagram of tin (Sn), [Kr] 4d10 5s2 5p2, with the krypton core drawn as one bar: one box per orbital, filled by Hund’s rule, showing two unpaired electrons, in 5p.
Orbital diagram of tin (Sn). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one tin atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

  1. one atom = 118.71 / (6.02214076 × 10²³)
  2. = 1.9712 × 10⁻²² g

Atoms in one gram

  1. atoms per gram = 6.02214076 × 10²³ / 118.71
  2. = 5.0730 × 10²¹ atoms

Tin on the periodic table

Tin is in period 5, group 14, in the p-block.

The other elements of group 14 are carbon, silicon, germanium, lead and flerovium.

The rest of period 5

Work with tin