The periodic table is an arrangement of the elements ordered by their atomic numbers. This arrangement groups elements with similar properties in the same column or row.
The horizontal rows in the periodic table are called periods. Periods reflect the number of electron shells an element has, with the first period having only one electron shell and the seventh period having seven electron shells.
The vertical columns in the periodic table are called groups. Groups categorize elements based on their properties and each group has a shared set of characteristics. For example, elements in the same group may have similar reactivity or valence electron configuration. The groups are numbered from 1-17