Oxygen (O)
Element 8 · reactive nonmetal · group 16, period 2
Oxygen is element 8, a reactive nonmetal in group 16 and period 2. Its electron configuration is [He] 2s2 2p4. That leaves 6 valence electrons in the outer shell, with the shells filling 2, 6. It is 2 electrons short of a full octet, so it gains them and carries a charge of -2.
- 8 protons
- 6 valence e−
- -2
- p-block
Oxygen Lewis dot structure
Oxygen has 6 valence electrons, so its Lewis symbol carries 6 dots: two pairs and two single dots. The dots go one to a side before any of them pair up, so the unpaired ones show exactly how many bonds the atom tends to form. The ion has gained 2 more to fill its shell, so all 8 are drawn as pairs.
Draw it in the Lewis structure generator →
Properties
| Atomic number | 8 |
|---|---|
| Symbol | O |
| Standard atomic weight | 15.999 u |
| Group | 16 |
| Period | 2 |
| Block | p-block |
| Category | reactive nonmetal |
| Electron configuration | 1s2 2s2 2p4 |
| Noble-gas notation | [He] 2s2 2p4 |
| Electrons per shell | 2, 6 |
| Valence electrons | 6 |
| Common ionic charge | -2 |
| Electronegativity (Pauling) | 3.44 |
| Protons / electrons | 8 / 8 |
Electron configuration of oxygen
Orbitals fill from the lowest energy upward. Writing that out for oxygen gives 1s2 2s2 2p4, which is 1s2 2s2 2p4 in plain text.
Everything up to He is the same as in that noble gas, so it is usually abbreviated to [He] 2s2 2p4. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 4 | 6 |
Oxygen ion charge
Oxygen commonly forms ions with a charge of -2.
It has 6 valence electrons, so it is 2 short of a full octet and 6 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.
Common questions
What is the Lewis dot structure of oxygen?
The symbol O with 6 dots, one for each valence electron: two pairs and two single dots. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one. The O2- ion is drawn in brackets with all eight, because it has gained 2.
How many valence electrons does oxygen have?
Oxygen has 6 valence electrons. For a main-group element the count is the group number minus 10, and oxygen is in group 16.
What is the electron configuration of oxygen?
1s2 2s2 2p4, or [He] 2s2 2p4 written from the previous noble gas. Orbitals fill lowest energy first.
What is the charge of oxygen?
Oxygen commonly forms ions with a charge of -2. With 6 valence electrons it is 2 short of an octet and 6 above an empty shell, so it takes whichever route is shorter.
How many protons, electrons and neutrons does oxygen have?
A neutral oxygen atom has 8 protons and 8 electrons. Its standard atomic weight is 15.999, so the most common isotope has about 8 neutrons.
Oxygen in Lewis structures
What the configuration above means in practice. Oxygen brings 6 valence electrons to each of these, and the working on every one of them starts by counting exactly that.
Nearby elements
See the ionic charge of every element →