1. periods are ____________ on the periodic table. left to right diagonals vertical columns horizontal rows…

1. periods are ____________ on the periodic table. left to right diagonals vertical columns horizontal rows right to left diagonals

1. periods are ____________ on the periodic table. left to right diagonals vertical columns horizontal rows right to left diagonals

Answer

Brief Explanations:

The periodic table is organized with periods as horizontal rows. Each period represents a new principal energy level for electrons.

Answer:

C. horizontal rows