L1 /
11
CH1012
RADII AND IE1-
PERIODS
• the atomic
and ionic radii decrease
going across a period because Zeff (effective
nuclear charge) increases
pulling in the outer valence
electrons.
• Ionisation energies (IE1): M(g) ® M+(g) + e-increase
going across a period, atoms get smaller
making valence e- harder to eject.
• Metal basicity reflects an ability to form stable cations & so a low IE1 favours basic cmpds. eg. Na ® Na2O2 ® Na+(aq) +
OH-
• Non-metal acidity reflects an ability to form covalently bound hydroxides, moderate IE1 & EA1 giving preference to covalent bonding. eg. P ® P2O5 ® H2PO4-(aq) + H+