Argon (Ar)
Element 18 · noble gas · group 18, period 3
Argon is element 18, a noble gas in group 18 and period 3. Its electron configuration is [Ne] 3s2 3p6. That leaves 8 valence electrons in the outer shell, with the shells filling 2, 8, 8. Its outer shell is already full, so it does not normally form ions at all.
- 18 protons
- 8 valence e−
- p-block
Properties
| Atomic number | 18 |
|---|---|
| Symbol | Ar |
| Standard atomic weight | 39.948 u |
| Group | 18 |
| Period | 3 |
| Block | p-block |
| Category | noble gas |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 |
| Noble-gas notation | [Ne] 3s2 3p6 |
| Electrons per shell | 2, 8, 8 |
| Valence electrons | 8 |
| Common ionic charge | none |
| Electronegativity (Pauling) | no accepted value |
| Protons / electrons | 18 / 18 |
Electron configuration of argon
Orbitals fill from the lowest energy upward. Writing that out for argon gives 1s2 2s2 2p6 3s2 3p6, which is 1s2 2s2 2p6 3s2 3p6 in plain text.
Everything up to Ne is the same as in that noble gas, so it is usually abbreviated to [Ne] 3s2 3p6. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 6 | 6 |
| 3s | 2 | 2 |
| 3p | 6 | 6 |
Argon ion charge
Argon does not normally form ions. Its outer shell is already full, so there is nothing to gain by losing or gaining an electron.
Common questions
How many valence electrons does argon have?
Argon has 8 valence electrons. For a main-group element the count is the group number minus 10, and argon is in group 18.
What is the electron configuration of argon?
1s2 2s2 2p6 3s2 3p6, or [Ne] 3s2 3p6 written from the previous noble gas. Orbitals fill lowest energy first.
How many protons, electrons and neutrons does argon have?
A neutral argon atom has 18 protons and 18 electrons. Its standard atomic weight is 39.948, so the most common isotope has about 22 neutrons.
Nearby elements
See the ionic charge of every element →