Does each element have a specific number of valence electrons? How can you figure out how many valence electrons an element's atoms have?

Detail is given below.

Explanation:

Each element have a specific number of valence electron. We can easily find out the number of valence electron in an atom through electronic configuration. The electrons reside in outer orbital are called valence electrons. It is also equal to the main group number of that element. Consider the example,

Sodium is present in group one thus it has 1 valence electron.

Electronic configuration of sodium:

Na₁₁ = 1s² 2s² 2p⁶ 3s¹

Let consider the example of halogens they are present in group 7A thus they have seven valence electrons.

Electronic configuration of fluorine:

F₉ = 1s² 2s² 2p⁵

The outer orbital contain seven electrons thus these are valance electron.

Copper is present in group 2B thus it must have two valence electrons.

Let check this from electronic configuration.

Cu₂₉ = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹

The outer most orbital is 4s² and it has two electron thus number of valence electron in copper are 2.