Question

What are the horizontal (from left to right) parts of the periodic table called?

rows
periods
families

Answer 1

It would be periods because they are also known as rows=Principal Energy Levels that hold electrons

Answer 2

The correct answer is periods. See the explanation below, please.

Step-by-step explanation:

The horizontal lines in the periodic table are called periods (ranging from 1 to 7) and vertical lines (ranging from 1 to 18).

The period that an element belongs to coincides with the last electronic layer of the element (that compound in period 3 will have 2 electronic layers).