Element 36 · Noble gas
Krypton (Kr) — Element 36
Greek kryptos — hidden
Krypton (Kr) is a noble gas in Period 4, Group 18 of the periodic table with atomic number 36, standard atomic weight 83.798 u, and ground-state electron configuration [Ar] 3d¹⁰ 4s² 4p⁶. At standard temperature and pressure it is classified as a gas with 0 valence electrons and common oxidation states 0.
Lighting, lasers, insulation
What are the atomic properties and physical constants of Krypton?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 36
- Standard atomic mass
- 83.798 u
- Chemical family
- Noble gas
- Ground-state configuration
- [Ar] 3d¹⁰ 4s² 4p⁶
- Electrons per shell
- 2, 8, 18, 8
- Valence electrons
- 0
- Common ion charges / oxidation states
- 0
- Phase at STP
- Gas
- Pauling electronegativity
- 3.00 Pauling
- First ionization energy
- 1,351 kJ/mol
- Atomic radius
- 88 pm
- Melting point
- -157 °C
- Boiling point
- -153 °C
- Discovery year
- 1898
- Table coordinate
- Period 4, Group 18
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Krypton’s shells?
A neutral Krypton atom contains 36 electrons distributed across 4 occupied principal energy shells ([Ar] 3d¹⁰ 4s² 4p⁶). The table below compares Krypton’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Kr | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 8 e⁻ | 32 e⁻ |
Frequently Asked Questions about Krypton (Kr)
What is the atomic mass and atomic number of Krypton (Kr)?
Krypton (Kr) has atomic number Z = 36 (36 protons in its nucleus) and an IUPAC standard atomic weight of 83.798 u. It sits in Period 4, Group 18 and is classified as a noble gas.
What is the ground-state electron configuration of Krypton?
The neutral ground-state electron configuration of Krypton (Z = 36) is [Ar] 3d¹⁰ 4s² 4p⁶. Across its 4 occupied principal shells (n = 1 to n = 4), the electrons per shell are 2, 8, 18, 8, with 0 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Krypton?
Krypton commonly forms 0 oxidation states or ion charges in compounds. Its Pauling electronegativity is 3.00 and its first ionization energy is 1,351 kJ/mol.
When was Krypton discovered and what is it used for?
Krypton was discovered in 1898 (Greek kryptos — hidden). Lighting, lasers, insulation
How does Krypton compare to neighboring elements?
Other noble gas elements: