Question

What does Valence mean in chemistry?

Answer 1

Valence is a term that deals with the electrons that are most typically involved in the bonding characteristics of an atom. These electrons are found in the s and p orbitals of the highest energy level of the electron configuration for the element.

The valence shell can hold 2 electrons in the s orbital representing the first two columns of the periodic table and 6 electrons in the p orbital found in columns 13 - 18 of the periodic table.

Some examples would include:

Mg `1s^2 2s^2 2p^6 3s^2` Magnesium has 2 valence electrons in the 3s orbital.

Se `[Ar] 4s^2 3d^10 4p^4` Selenium has 6 valence electrons in the 4s and 4p orbitals.

Each element in the periodic table will have the same number of valence electrons as the elements in the same column. All Alkai Metals (Li, Na, K, Rb) have 1 valence electron. All Halogens (F.Cl, Br, I) have 7 valence electrons. All of the Noble Gases (Ne, Ar, Kr Xe) will have 8 valence electrons and fulfill the `Rull of Octet`.

Atoms try to gain or lose electrons to fulfill the `Rule of Octet` for the 8 electrons that can fill the s and p orbitals. An atom can take on electrons and become an negatively charged anion or can lose electrons and become a positively charged cation. Or atoms can share valence electrons during bonding.

I HOPE THIS WAS HELPFUL.
SMARTERTEACHER