Does chlorine have a small atomic radius, or a large atomic radius?
That is a tough question to answer. First of all, radius is singular, while radii is plural. Atomic radii tend to decrease as you move to the right across a row, while they increase as you go down a column. It should also be noted that the chloride ion will have a larger radius than a chlorine atom involved in a covalent bond (as another general rule, anions are larger than cations.) Examples: H < Li < Na < K < Rb < Cs < Fr Li > Be > B > C > N > O > F Cl- > Cl; K+ < K The above examples should give you a good idea for the trends. The first series shows increasing radius down a column; the second series shows decreasing radius across a row. The last examples show that an anion is larger than the atom from which it was formed, while cations are smaller than their parent atoms.
