3683.798KrKrypton
Krypton (Kr) — element 36noble gas · group 18, period 4
Krypton is a chemical element with the symbol Kr and atomic number 36. It is a noble gas in group 18, period 4 of the periodic table (the p-block), with a standard atomic mass of 83.798 u. At room temperature (25 °C) krypton is a gas.
💡 Known for: A noble gas used in high-performance lighting; a krypton spectral line defined the metre from 1960 to 1983.
# Krypton properties
| Symbol | Kr |
|---|---|
| Atomic number | 36 |
| Atomic mass | 83.798 u |
| Category | noble gas |
| Group | 18 |
| Period | 4 |
| Block | p-block |
| Electron configuration | [Ar] 3d¹⁰ 4s² 4p⁶ |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ |
| Electrons per shell | 2, 8, 18, 8 |
| Protons / electrons | 36 / 36 |
| State at 25 °C | gas |
| Melting point | 115.79 K (-157.4 °C, -251.2 °F) |
| Boiling point | 119.93 K (-153.2 °C, -243.8 °F) |
| Density | 3.733 g/L |
| Electronegativity (Pauling) | 3 |
| First ionization energy | 14.0 eV |
| Atomic radius | 88 pm |
| Discovered | 1898 |
# Electron configuration of krypton
The electron configuration of krypton is [Ar] 3d¹⁰ 4s² 4p⁶, written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶. Its 36 electrons fill 4 shells as 2, 8, 18, 8, so the outermost shell holds 8 electrons. As a group 18 element, krypton has 8 valence electrons.
# Related elements
BrBromineprevious elementRbRubidiumnext elementHeHeliumgroup 18NeNeongroup 18ArArgongroup 18XeXenongroup 18RnRadongroup 18OgOganessongroup 18
# Krypton FAQ
What is the atomic number of krypton?
The atomic number of krypton is 36: every krypton atom has 36 protons in its nucleus. Its symbol is Kr.
What is the atomic mass of krypton?
The standard atomic mass of krypton is 83.798 u.
What is the electron configuration of krypton?
Krypton's electron configuration is [Ar] 3d¹⁰ 4s² 4p⁶ (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶), with 2, 8, 18, 8 electrons per shell.
Is krypton a metal?
No. Krypton is a noble gas, a nonmetal.
What is the melting point of krypton?
Krypton melts at 115.79 K (-157.4 °C, -251.2 °F) and boils at 119.93 K (-153.2 °C, -243.8 °F).
What is krypton used for / known for?
A noble gas used in high-performance lighting; a krypton spectral line defined the metre from 1960 to 1983.