In periods generally boiling point goes on:

Explanation

Across the short periods, the melting and boiling points of elements increase with the number of valence electrons upto group IVA and then decreaseupto the noble gases. The melting points of group IA elements are low because each atom in them provides only one electron to form a bond with other atom. Melting points of group IIA elements are considerably higher than those of group IA elements because each atom in them provides two binding electrons. Since carbon has the maximum number of binding electrons, thus it has a very high melting point in diamond in which each carbon is bound to four other carbon atoms. In general, the elements whichexist as giant covalent structures have very high melting points.