How does the covalent radius change as you move down a group in the periodic table?

As you move down a group in the periodic table, the number of electron shells increases. Each successive element in a group has an additional electron shell compared to the one above it. This increase in the number of shells means that the outermost electrons are farther from the nucleus.

The covalent radius refers to the size of an atom when it forms covalent bonds, and this size increases as the distance from the nucleus to the outermost electrons becomes greater due to the addition of more shells. This phenomenon results in a greater atomic size as the outer electrons are less tightly held by the nucleus because they are farther away, and this effectively increases the covalent radius.

In summary, the covalent radius increases down a group primarily because additional electron shells lead to an increase in atomic size, which affects how atoms bond with one another.