Krypton (Kr)
Krypton is element 36, a noble gas in group 18, period 4. A neutral atom has 36 protons, 48 neutrons and 36 electrons, 8 of them valence electrons.
Noble gas- Atomic number
- 36
- Atomic mass
- 83.8 u
- Valence electrons
- 8
- Protons · neutrons
- 36 · 48
- Electrons per shell
- 2, 8, 18, 8
- At room temperature
- gas
Bohr model of krypton
The Bohr model draws krypton as a nucleus of 36 protons and 48 neutrons, with its 36 electrons on 4 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 8 in shell 4. Press Build the atom to watch the shells fill from the inside out. The outer ring (the N shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of krypton
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶
Short form (noble gas notation): [Ar] 4s² 3d¹⁰ 4p⁶. The [Ar] stands for the electrons of argon, the noble gas before it.
How many valence electrons does krypton have?
Krypton has 8 valence electrons.
Krypton is in group 18, and for groups 13–18 you subtract 10 from the group number: 18 − 10 = 8. A full outer shell of eight makes it a noble gas that rarely reacts.
Protons, neutrons and electrons
| Protons | 36 | equal to the atomic number |
|---|---|---|
| Electrons | 36 | equal to the protons in a neutral atom |
| Neutrons | 48 | mass number 84 − 36 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Krypton properties
| Symbol | Kr |
|---|---|
| Category | Noble gas |
| Group · period · block | 18 · 4 · p |
| Atomic mass | 83.8 u |
| State at 25 °C | gas |
| Melting point | 115.8 K (-157 °C, -251 °F) |
| Boiling point | 119.9 K (-153 °C, -244 °F) |
| Density | 0.0037 g/cm³ |
| Electronegativity (Pauling) | 3 |
| Atomic radius | 202 pm |
| First ionization energy | 14 eV |
| Electron affinity | — |
| Oxidation states | 0 |
| Common ion charge | 0 |
| Discovered | 1898 by William Ramsay |
Where krypton sits on the periodic table
Group 18: Helium, Neon, Argon, Xenon, Radon, Oganesson.
Questions about krypton
How many valence electrons does krypton have?
Krypton has 8 valence electrons.
How many protons, neutrons and electrons does krypton have?
A neutral krypton atom has 36 protons and 36 electrons. Its most common form has about 48 neutrons (mass number 84 − 36 protons).
What is the electron configuration of krypton?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶, written in short form as [Ar] 4s² 3d¹⁰ 4p⁶.
What does the Bohr model of krypton look like?
A nucleus of 36 protons and 48 neutrons, circled by 4 electron shells holding 2, 8, 18, 8 electrons.
What is the atomic number of krypton?
36. The atomic number is the number of protons in the nucleus, and it is what makes an atom krypton.