NO. 001Reactive Nonmetal

H

Hydrogen

Hydrogen is the lightest element and is the most abundant chemical element in the universe, constituting about 75% of all normal matter.

Crystal Structure

Hexagonal close-packed (hcp)

Atomic Mass1.008 u

Density0.00008988 g/cm³

Melting Point13.99 K

Boiling Point20.271 K

Atomic Radius53 pm

Electronegativity2.2

Ionization Energy1312 kJ/mol

Electron Affinity72.8 kJ/mol

Bonding TypeCovalent

Oxidation States1, -1

Acid/BaseCan act as acid or base

ReactivityHigh

Electron Configuration

1s1

Discovered ByHenry Cavendish

Year1766

Known Isotopes

H-1(Protium)H-2(Deuterium)H-3(Tritium)