Question

There are seven ___ included in the periodic table.

Answer 1

The periodic table has seven horizontal rows called periods. Each period represents a different energy level of the electron shells. The first period has 2 elements (hydrogen and helium) and the subsequent periods each have 8 elements.

Step-by-step explanation:

The periodic table has seven horizontal rows called periods. The elements are arranged in these periods based on their atomic number and electron configurations. Each period represents a different energy level of the electron shells. The first period has 2 elements (hydrogen and helium) and the subsequent periods each have 8 elements. In total, there are 7 periods on the periodic table.