The diagram to the right shows a plausible series of atomic radii for a column of the periodic table. Given the concepts of atomic orbitals and multi$-$electron interactions we have discussed, state whether the the general trend for each property below will INCREASE or DECREASE. Choose and briefly justify your answer.

EXAMPLE: The energy to remove one electron from an atom.

ANSWER: Energy will DECREASE because the valence electrons will be more shielded, and thus experience a lower $Z_{\text{e}\text{f}\text{f}}$

a$)$ The average radial distance of an electron in a $1s$ orbital.

b$)$ The average radial distance of an electron in the valence shell.

Atomic Radius

Increasing

principal

quantum

number, $n$