Page 9 - classification of elements

Valence shell: The outermost shell of an atom is called valence

shell.

Core shells: The shells inner to the valence shell are called core

shell.

Valence electrons: The electrons that lies on the valence shell of

an atom are called valence electron.

For example:

electronic configuration of magnesium is:

2
2
1s 2s 2p 6 3s 2

core of atom valence shell

Isolated Stornium

atom in electric field