Question

How is valency related to atomic structure

Answer 1

All the atoms combine with other to gain stability of nearest inert gases by either loosing electron or by gaining electron.
Hence combining capacity of atom is defined as valency.
For example oxygen
atomic number 8 means 8 protons and 8 electrons.
electronic configuration 1s2 2s2 2p4.
valence electrons are 6
hence it gains two electrons to get neon gas stability.
hence its valency is 2.