Period (periodic table)

A period in the periodic table is any horizontal row of elements.

Each elements in the same period has one more proton than the one to its left. This means its atomic number is one number higher. The elements in the same period are very metallic on the left and nonmetallic on the right. The smaller atoms are on the left and the larger ones are on the right because the atoms have more protons and electrons.

The first period has 2 elements, hydrogen and helium. The second period and third period each have 8 elements. The fourth period and fifth period each have 18 elements. The sixth period and seventh period each have 32 elements. F-block elements are counted in the sixth and seventh periods. Hence, each one has 32 elements in it.