CH1012
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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+