Krypton (Kr)
Element 36 · Noble gas · Gas at 25 °C · Group 18, Period 4
Krypton fills high-performance flash lamps and some insulated windows; from 1960 to 1983 the meter itself was defined by the orange light of a krypton lamp.
On the periodic table, krypton sits in group 18 — the noble gases — in period 4. It is one of 7 elements classified as a noble gas, and at room temperature (25 °C) it is a gas — one of 11 elements that are gases at room temperature.
The noble gases of group 18 have completely filled outer electron shells, so they have almost no urge to react with anything. All the naturally occurring members are colorless, odorless, monatomic gases at room temperature. Their aloofness is useful in its own right — inert atmospheres, lighting, and cryogenics all rely on it.
Properties of krypton
| Atomic number (Z) | 36 |
|---|---|
| Symbol | Kr |
| Atomic mass | 83.798 |
| Category | Noble gas |
| Group | 18 |
| Period | 4 |
| Block | p-block |
| Metal / nonmetal | Nonmetal |
| State at 25 °C | Gas |
| Electron configuration | [Ar] 3d10 4s2 4p6 |
| Electronegativity (Pauling) | 3 |
| Melting point | -157.36 °C (115.79 K / -251.25 °F) |
| Boiling point | -153.22 °C (119.93 K / -243.8 °F) |
| Density | 0.003733 g/cm³ |
Position in the periodic table
Krypton shares group 18 — the noble gases with Helium (He), Neon (Ne), Argon (Ar), Xenon (Xe), Radon (Rn), Oganesson (Og). Elements in the same group have the same number of outer electrons, so they tend to behave alike chemically — comparing them is one of the fastest ways to see periodic trends in action.
Within this dataset, it ranks #5 in electronegativity out of 99 elements with a pauling value.
Physical properties
Krypton melts at -157.36 °C (115.79 K / -251.25 °F) and boils at -153.22 °C (119.93 K / -243.8 °F), giving it a liquid range of about 4.1 °C at standard pressure.
As a gas at standard conditions, its density is 0.003733 g/cm³ — measured at STP like the other gaseous elements here.
See also: the interactive periodic table, how to read the periodic table, the element families tour.