Period (periodic table) facts for kids
A period in the Periodic Table is any horizontal row of elements. The elements in a certain period all increase one by one in atomic numbers. The elements in the same period are very metallic on the left, and nonmetallic on the right. As you go across a period towards the right, the size of the atom gets larger, because protons and electrons are increasing.
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In the periodic table of the elements, each numbered row is a period.
Period (periodic table) Facts for Kids. Kiddle Encyclopedia.