Talk:IB Chemistry/Periodicity

"Negative ions (F + e- ‡ F-) have larger radii because the positive charge of the nucleus has less positive pulling power (PPP) due to the presence of an extra electron in this ionic state."

How can this statement be justified? - Whilst there is a repulsion effect in each of the three P orbitals, 2 of these orbitals are already occupied in fluorine, so the attraction to all 3 second P orbitals should be identical and the attractions will be the same. What evidence is there that the P orbitals are altered by the addition of an electron?

According to my data book, which uses the Pauling index, the van der Waals radius for oxygen (0.150 nm) is greater than the anion radius (0.140 nm). Other indices give a yet smaller ionic radius for O. Comparisons with covalent radii are useless as these involve different bonding orbitals.

In any case; "larger" than what? Ionic radii can only be estimates as they cannot be measured independently of other ions. The criteria for all other radii measurements (covalent, van der Waals and metallic) are all different, so comparisons are meaningless. (Martin Bennett - Havant)