Valence Electrons

Valence electrons are the electrons in the outermost shell.
  1. The electrons in the outermost shell of an atom are called valence electrons.
  2. The valence electrons have great significance in determining the chemical properties of an atom.
  3. Elements with the same number of valence electron have the same chemical properties.


Example:
Given that a sodium atom has 11 protons 12 neutrons. Find the number of valence electron in a sodium atom.

Answer:
For an atom,

Number of electrons = number of protons = 11

Electron arrangement of sodium = 2.8.1

Therefore, sodium has 1 valence electron.