Question

along each row of the periodic table,
a. atomic mass increases from left to right.
b. atomic mass decreases from left to right.
c. atomic mass is the same for all elements in the row.
d. atomic mass changes in no set pattern.

Explanation:

In the periodic table, as you move from left - to - right along a row (period), the atomic number increases by 1 for each successive element. Since the atomic mass is related to the number of protons, neutrons, and electrons in an atom, and as the atomic number increases, the number of protons and usually neutrons also increases. So, the atomic mass generally increases from left to right along a row.

Answer:

A. atomic mass increases from left to right.