Periodicty Flashcards
Why does melting point increase across period 3 from Na to Al
Charge increases from 1+ to 3+ so number of free e- increases and strength of metallic bond increases
Size decreases with charge
Bonding of Si
Macromolecular
List P, S, Cl, and Ar in order of highest melting point to lowest
S8>P4>Cl2>Ar
Trend in atomic radius down a group
Increases
Trend in atomic radius across a period
Why?
Decreases
Nuclear charge increases but shielding stays the same
e- more strongly attracted to nucleus
Trend in ionisation energy down a group
Decreases e- removed from higher PEL e- further from nucleus More shielding Weaker attraction and less energy required
Trend in ionisation energy across a period
Increases Proton number increases Constant shielding Radius decreases More energy required
Why is 1st ionisation energy of Al lower than Mg
e- removes from higher energy PEL so less energy required to remove it
Why is 1st IE lower for S than P
Pair of e- in p-orbital
Extra repulsion
Less energy required
