Use the drop-down menus to complete the statements. a vertical column of elements in the periodic table is called a . a horizontal row of elements in the periodic table is called a . atoms of elements in the same group have the same . as you move from left to right on the periodic table, the atomic number .

1) group

2) period

3) numbers of valence electrons

4) increases

Explanation:

When we move in a periodic table from top to bottom or vice versa along a vertical column , it is said that we are moving along a "group" in a periodic table.

Like wise when we move in a periodic table from left to right or right to left  in a horizontal row , it is said that we are moving along a "period" in a periodic table.

The classification of elements belonging to any specific group of periodic table is dependent on the total number of valence electron. All elements of with in a group have same number of valence electrons however, the orbitals may change.

The atomic number increases while moving from left to right as the number of orbitals in which the valence electron is found also increase in the same direction.