The number of elements present in each normal periods is __________.

A period is a row of the periodic table that is horizontal. The periodic table contains seven periods, each of which starts at the very left. When a new primary energy level starts to fill up with electrons, a new period starts. There are only two elements in period 1 (hydrogen and helium), compared to eight elements in periods 2 and 3. The elements in periods 4 and 5 total 18. The two bottom rows that are isolated from the rest of the table and comprise Periods 6 and 7 have 32 components each. They are removed to allow the table to be more readily fit on a single page.

Hence, the required answer is 18.