Si has the highest melting point because of it's giant covalent structure. Na,Mg,Al have a metallic structure which require less energy to overcome intermolecular forces of the other elemnts simple molecular structures.
Period 3 exceptions in ionisation energies
There is an overall increase in ionisation energies across the period, but Mg (3s2)has a high IE than Al (3p1), and P (3p3) has a higher IE than S (3p4).
Factors of ionisation energy:
nuclear charge
distance from nucleus (attraction)
shielding (increases down a group, stays the same across a period)
Atomic radius increases/decreases down a group and increases/decreases across a period.
increases, decreases
Ionisation energy trend in period 2
Ionisation energy overall increases across a period, but exceptions where Be has a higher IE than B, and N has a higher IE than O.
