AFOQT Practice Test

How does the atomic mass change in the periodic table?

1. Increases from right to left and top to bottom

2. Increases from left to right and top to bottom

3. Stays constant across periods

4. Varies randomly

The correct answer is: Increases from left to right and top to bottom

The atomic mass of elements in the periodic table typically increases from left to right across a period and from top to bottom down a group. This pattern occurs because as you move from left to right, each subsequent element has more protons and neutrons, which contributes to an increase in atomic mass. Similarly, as you descend a group, additional electron shells are added, along with more protons and neutrons, further increasing the atomic mass. Elements on the right side of the periodic table have higher atomic numbers compared to those on the left, resulting in higher atomic masses. Additionally, the tendency for atomic mass to increase down a group is due to the added mass from the incoming additional layers of electrons and corresponding protons and neutrons. Thus, the observed pattern is one of a steady increase in atomic mass as you move right and down the periodic table.