Kr
Krypton
Element 36 · Noble gas
Krypton (Kr)
Krypton is a colourless, odourless noble gas found in trace amounts in air. It glows whitish when electrified.
- Noble gas
- Period 4
- Group 18
- p-block
- gas at room temperature
Key properties
- Atomic mass
- 83.8
- u
- Electron configuration
- [Ar] 3d10 4s2 4p6
- Melting point
- -157.4 °C
- 115.79 K
- Boiling point
- -153.2 °C
- 119.93 K
- Density
- 3.733 g/L
- Electronegativity
- 3
- Pauling
- Atomic radius
- 202 pm
- van der Waals
- 1st ionisation energy
- 14 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about krypton
- 01
From 1960 to 1983 the metre was defined by the wavelength of light from krypton-86.
- 02
Unlike Superman’s kryptonite, krypton is a perfectly harmless gas.
- 03
Krypton forms a few compounds, such as krypton difluoride.
Applications
What is krypton used for?
- Energy-efficient window insulation
- Photographic flash lamps
- Excimer lasers
- High-performance light bulbs
History
Discovery & name origin
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 36
- Atomic mass
- 83.8 u
- Group
- 18
- Period
- 4
- Block
- p-block
- Electron configuration
- [Ar] 3d10 4s2 4p6
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
- Electrons per shell
- 2, 8, 18, 8
- Electronegativity (Pauling)
- 3
- Electron affinity
- —
- Atomic radius (van der Waals)
- 202 pm
- Stable isotopes
- 5
Oxidation states
Highlighted: common oxidation states (0).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st1,350.8
- 2nd2,350.4
- 3rd3,565
- 4th5,070
- 5th6,240
- 6th7,570
- 7th10,710
- 8th12,138
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °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
- Molar heat capacity
- —
- Appearance
- Colourless gas, exhibiting a whitish glow in a high electric field
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Krypton questions
What is Kr on the periodic table?
Kr is the symbol for krypton, element 36 on the periodic table. It sits in group 18, period 4, in the noble gas category, and has an atomic mass of 83.8.
What is the atomic number of krypton?
Krypton has atomic number 36, so every krypton atom has 36 protons in its nucleus. Its symbol is Kr and its atomic mass is 83.8.
Who discovered krypton?
Krypton was discovered by William Ramsay and Morris Travers in 1898 (England). The name comes from Greek kryptos, “hidden”.
What is krypton used for?
Krypton is used for: energy-efficient window insulation; photographic flash lamps; excimer lasers; high-performance light bulbs.
Is krypton a metal?
No. Krypton is classed as a noble gas.
What is the electron configuration of krypton?
The electron configuration of krypton is [Ar] 3d10 4s2 4p6. Its 36 electrons are arranged in shells as 2, 8, 18, 8.