How many valence electrons are present in an atom?

Answer 1

The number of valence electrons is the same number as the column of on the Periodic Table. Hydrogen has one, Calcium has two, etc. However, Helium may only have 2 and is an exception and Boron only wants 6 to fill its octet.

Answer 2

The number of valence electrons in an atom is determined by its group number in the periodic table. For main group elements (groups 1, 2, 13-18), the number of valence electrons is equal to the group number. Transition metals have variable numbers of valence electrons.

Answer 3

The valence of an atom depends on the element type. For example, the valence for Carbon, a group 14 element, is four.

Answer 4

Valence is a concept relating to the formal charge of the atom; it isn't "composed" of anything.

Answer 5

The number valance electrons are not same in all elements. The number electrons present in the last shell refers to valence electrons.