Atomic Number
8
Element 8
Oxygen (O)
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal.
Atomic Mass
15.999 u
Category
Nonmetal
Period
2
Group
Group 16: oxygen group
Phase
gas
Density
0.001429 g/cm3
Electron Shells
2, 6
Atomic Structure
Protons: 8. Electrons: 8. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁴
Why Oxygen Matters
Oxygen helps connect atomic number 8, nonmetal behavior, period 2 trends, and electron shell structure. Its gas phase, atomic mass of 15.999 u, and electron configuration 1s² 2s² 2p⁴ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Oxygen was discovered 1771 by Carl Wilhelm Scheele. Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal.
Safety and Handling Context
Oxygen is a gas at standard conditions. Gas cylinders and concentrated gases should be handled only with proper ventilation and equipment.
Related Elements
Frequently Asked Questions
- What is the atomic number of Oxygen?
- Oxygen has atomic number 8, which means a neutral atom has 8 protons and 8 electrons.
- What is the chemical symbol for Oxygen?
- The chemical symbol for Oxygen is O.
- What category is Oxygen in?
- Oxygen is classified as a nonmetal and sits in period 2 of the periodic table.
Explore Oxygen in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Oxygen to neighboring elements without losing your place.