Argon (Ar)
18ArArgon39.948
Argon is element 18, a noble gas in period 3, group 18 of the periodic table. At room temperature it is a gas.
Electron configuration [Ne] 3s2 3p6
Electrons per shell 2, 8, 8
Argon data
| Atomic number | 18 |
|---|---|
| Symbol | Ar |
| Atomic mass | 39.948 u |
| Category | Noble gas |
| Group | 18 |
| Period | 3 |
| Block | p |
| State at 25 °C | gas |
| Melting point | 84 K (-189.1 °C) |
| Boiling point | 87 K (-186.1 °C) |
| Density | 0.001784 g/cm³ (1.784 g/L) |
| Electronegativity (Pauling) | — |
| Atomic radius | 97 pm |
| 1st ionization energy | 1521 kJ/mol |
| Electron affinity | 0 kJ/mol |
| Oxidation states | 0 |
| Common ion charge | 0 |
| Discovered | 1894 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
↑↓
1s↑↓
2s↑↓↑↓↑↓
2p↑↓
3s↑↓↑↓↑↓
3pWork through argon’s configuration and its ions →
Where argon sits
Argon belongs to the noble gases. To use its mass in a calculation, try the molar mass calculator.
Argon FAQ
What is the electron configuration of argon?
Argon (Z = 18) has the configuration 1s2 2s2 2p6 3s2 3p6. In noble-gas shorthand that is [Ne] 3s2 3p6.
How many valence electrons does argon have?
8 (full outer shell).
What is the atomic mass of argon?
The standard atomic weight of argon is 39.948 u, so one mole weighs 39.948 g.
Is argon a metal?
No. Argon is a noble gas.
What is the charge of a argon ion?
Argon most commonly forms no ions.