Periodicity of period 3

The elements in period 3 are ( going from left to right) : Na, Mg, Al, Si, P, S, Cl,Ar.

Going from left to right their atomic radii become smaller as proton number increases (which makes nuclear firce increase and therefor "pull" the electron closer. 

Melting points : The melting points increase across the period unti it reaches a sharp peak at Silicon where it has a big drop to Phosphorus and it gradually decreases from there. 

The melting points of the…