Question

How do the number of valence electrons an element has change from column to column?

Answer 1

It increases by one to the right and decreases by one to the left, except transition elements
(first column always has 1 valence electron)

column refers to groups, so group 1 has 1 valence electron, group 2 has 2 valence electron and so on

Answer 2

Increases by an unit.

Step-by-step explanation:

The periodic table refers to the table in which the chemical elements are arrangement in the increasing order of their atomic number (Z). This table contains 18 vertical columns, known as groups and 7 horizontal rows, called columns.

As we move across the period, i.e. left to right from one column to another; the number of valence electrons in the valence shell of a chemical element progressively increases by an unit.