Question

how do elements change as you move to the right along a row in the periodic table? the atomic number decreases. the electronegativity decreases. the average atomic mass increases. the number of valence electrons decreases.

Explanation:

As you move from left - to - right across a period (row) in the periodic table, the atomic number increases as the number of protons in the nucleus increases. The electronegativity generally increases. The average atomic mass also increases due to the increase in the number of protons, neutrons. The number of valence electrons increases from 1 to 8 across a period.

Answer:

The average atomic mass increases.