# Question #fe5fc

Jan 29, 2015

The horizontal rows of the periodic table are called periods.

The first period of the periodic table has just two elements, $\text{H}$ and $\text{He}$. As you go down the periodic table, the number of elements in a period increases.

As you can see in the image, the periodic table has 7 periods. As a side note, the vertical rows are called groups - there are 18 of those in the periodic

Sep 12, 2015

The horizontal rows on the periodic table are called periods.

#### Explanation:

The periodic table consists of seven rows called periods, and 18 columns called groups or families. The properties of the elements within a period vary across the periodic table in predictable ways, while the elements within a group have similar properties.