Helium (He)

Helium is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table.

Atomic Number

2

Atomic Mass

4.0026 u

Category

noble gas

Phase

gas

Density

0.0001785 g/cm³

Electron Shells

2

Atomic Structure

Protons: 2 • Electrons: 2 • Neutrons: Varies by isotope

Electron Configuration: 1s²

Discovery

1868 • Pierre Janssen, Norman Lockyer