Question

how does atomic radius change from left to right across a period in the periodic table?
it tends to decrease.
it tends to increase.
it first decreases, then increases.
it first increases, then decreases.

Explanation:

As we move from left to right across a period in the periodic table, the number of protons in the nucleus increases. This leads to a greater positive charge in the nucleus. At the same time, the electrons are added to the same outermost shell. The increased nuclear charge pulls the electrons closer to the nucleus. So, the atomic radius tends to decrease.

Answer:

It tends to decrease.