Electronic configuration of phosphorus

Electrons in each shell

Phosphorus has 15 electrons arranged as 2, 8, 5 across 3 shells, which is why it sits in period 3.

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 Phosphorus's 15 electrons in that order gives 1s² 2s² 2p⁶ 3s² 3p³.

Phosphorus at a glance

Atomic number	15
Symbol	P
Atomic mass	30.974 u
Group	15
Period	3
Block	p-block
Category	Non-metal
Valence electrons	5

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Other elements in group 15

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