Question

1. choose the best answer. atomic masses __ across a period and __ down the periodic table. increase, decrease decrease, decrease increase, increase decrease, increase

Explanation:

As you move across a period (from left - to - right) in the periodic table, the atomic number increases, and with more protons and neutrons in the nucleus, the atomic mass increases. As you move down a group (top - to - bottom), new electron shells are added, and the number of protons, neutrons, and electrons increases, leading to an increase in atomic mass.

Answer:

C. increase, increase