004Alkaline earth metal · Group 2 · Period 2

Beryllium

Beryllium (Be) is element 4, a alkaline earth metal in the s-block — group 2, period 2. It is a solid at room temperature with 2 electron shells (2, 2) and an atomic mass of 9.01218315 u.

Atomic mass: 9.012 u
Phase · STP: solid
Melting: 1560 K · 1287 °C
Boiling: 2742 K · 2469 °C
Electronegativity: 1.57
Density: 1.85 g/cm³

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Identity

Atomic number: 4
Standard atomic weight: 9.012 u
Category: Alkaline earth metal
Group: 2 · Alkaline earth metals
Period: 2
Block: s-block
Oxidation states: +2

Physical properties

Melting point: 1560 K · 1287 °C
Boiling point: 2742 K · 2469 °C
Density: 1.85 g/cm³
Molar heat capacity: 16.443 J/(mol·K)
Atomic radius: 153 pm
Electron affinity: -48 kJ/mol

Atomic structure

4protons

5neutrons

4electrons

2valence e⁻

Noble-gas notation: [He] 2s2
Full configuration: 1s2 2s2
Electrons per shell: 2, 2

Periodic trends

Where Beryllium ranks across all 118 elements.

Electronegativity1.57

Ionization energy899.5 kJ/mol

Electron affinity-48 kJ/mol

Density1.85 g/cm³

Atomic radius153 pm

Ionization energies

Energy to remove each successive electron (kJ/mol).

899.5

1.8k

14.8k

21.0k

Successive ionization energies (kJ/mol, log scale).

Discovery

Discovered: 1798
Discovered by: Louis Nicolas Vauquelin
Named by: —
Appearance: white-gray metallic