Electronic configuration of beryllium

Electrons in each shell

Beryllium has 4 electrons arranged as 2, 2 across 2 shells, which is why it sits in period 2.

How to write it

Electrons fill orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p… Each s orbital holds 2 electrons, p holds 6 and d holds 10. Placing Beryllium's 4 electrons in that order gives 1s² 2s².

Beryllium at a glance

Atomic number	4
Symbol	Be
Atomic mass	9.0122 u
Group	2
Period	2
Block	s-block
Category	Alkaline earth metal
Valence electrons	2

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Other elements in group 2

Elements in the same group have the same number of outer electrons, which is why they behave alike.