In the periodic table, elements are arranged in periods, which are horizontal rows. The properties of elements gradually change across a period from left to right.
The correct answer is period. The properties of elements gradually change across a period in a predictable way.
The correct answer is "period." In the periodic table, elements are arranged in periods and groups. A period is a row of elements that share the same energy levels. As you move across a period from left to right, the properties of the elements gradually change in a predictable way. This change occurs because the number of protons (atomic number) increases, which affects the arrangement of electrons and the overall chemical behavior of the elements.
