Oxygen (O)
Oxygen is element 8, a nonmetal in group 16, period 2. A neutral atom has 8 protons, 8 neutrons and 8 electrons, 6 of them valence electrons.
Nonmetal- Atomic number
- 8
- Atomic mass
- 15.999 u
- Valence electrons
- 6
- Protons · neutrons
- 8 · 8
- Electrons per shell
- 2, 6
- At room temperature
- gas
Bohr model of oxygen
The Bohr model draws oxygen as a nucleus of 8 protons and 8 neutrons, with its 8 electrons on 2 circular shells: 2 in shell 1, 6 in shell 2. Press Build the atom to watch the shells fill from the inside out. The outer ring (the L 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 oxygen
1s² 2s² 2p⁴
Short form (noble gas notation): [He] 2s² 2p⁴. The [He] stands for the electrons of helium, the noble gas before it.
How many valence electrons does oxygen have?
Oxygen has 6 valence electrons.
Oxygen is in group 16, and for groups 13–18 you subtract 10 from the group number: 16 − 10 = 6. It tends to gain 2 electrons to complete an octet, forming a −2 ion.
Protons, neutrons and electrons
| Protons | 8 | equal to the atomic number |
|---|---|---|
| Electrons | 8 | equal to the protons in a neutral atom |
| Neutrons | 8 | mass number 16 − 8 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.
Oxygen properties
| Symbol | O |
|---|---|
| Category | Nonmetal |
| Group · period · block | 16 · 2 · p |
| Atomic mass | 15.999 u |
| State at 25 °C | gas |
| Melting point | 54.36 K (-219 °C, -362 °F) |
| Boiling point | 90.2 K (-183 °C, -297 °F) |
| Density | 0.0014 g/cm³ |
| Electronegativity (Pauling) | 3.44 |
| Atomic radius | 152 pm |
| First ionization energy | 13.618 eV |
| Electron affinity | 1.461 eV |
| Oxidation states | −2 |
| Common ion charge | −2 |
| Discovered | 1774 by Carl Wilhelm Scheele |
Where oxygen sits on the periodic table
Group 16: Sulfur, Selenium, Tellurium, Polonium, Livermorium.
Questions about oxygen
How many valence electrons does oxygen have?
Oxygen has 6 valence electrons.
How many protons, neutrons and electrons does oxygen have?
A neutral oxygen atom has 8 protons and 8 electrons. Its most common form has about 8 neutrons (mass number 16 − 8 protons).
What is the electron configuration of oxygen?
1s² 2s² 2p⁴, written in short form as [He] 2s² 2p⁴.
What does the Bohr model of oxygen look like?
A nucleus of 8 protons and 8 neutrons, circled by 2 electron shells holding 2, 6 electrons.
What is the atomic number of oxygen?
8. The atomic number is the number of protons in the nucleus, and it is what makes an atom oxygen.