Relative trend in melting point of period 3 elements.Explain.

Element Proton number Symbol Melting point
(K) Boiling point
(K)
Sodium 11 Na 371 1156
Magnesium 12 Mg 922 1380
Aluminium 13 Al 933 2740
Silicon 14 Si 1683 2628
Phosphorus 15 P 317 553
Sulfur 16 S 392 718
Chlorine 17 Cl 172 238
Argon 18 Ar 84 87