Krypton (symbol Kr, atomic number 36) is a noble gas used in high-performance lighting and once to define the metre. It is classified as a noble gas and sits in group 18, period 4 of the periodic table.
Overview
Krypton is the chemical element with atomic number 36 and the symbol Kr. With a standard atomic weight of 83.798, it is a noble gas. In the periodic table it occupies group 18 and period 4, and under standard conditions it is normally a gas. Krypton is a noble gas used in high-performance lighting and once to define the metre.
Atomic structure
An atom of Krypton has 36 protons in its nucleus and, when neutral, 36 electrons arranged in the configuration [Ar] 3d10 4s2 4p6. Its standard atomic weight of 83.798 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Krypton was discovered in 1898 by William Ramsay, Morris Travers. It follows Bromine (Br) and precedes Rubidium (Rb) in order of atomic number.
| Atomic number | 36 |
|---|---|
| Symbol | Kr |
| Atomic mass | 83.798 |
| Category | Noble gas |
| Group | 18 |
| Period | 4 |
| Electron configuration | [Ar] 3d10 4s2 4p6 |
| Phase at STP | Gas |
| Discovered | 1898 (William Ramsay, Morris Travers) |