periodicity: melting point

Question 1

what is melting point?

Answer 1

the temperature at which a solid changes into a liquid

Question 2

melting points of Na, Mg and Al

Answer 2

Na, Mg and Al have giant metallic structures.
from Na to Al, no. of valance electrons increase and strength of metallic bonds increases > mp increases
highly charged Al3+ ion tends to attract electrons to itself and no. of valence electrons available for delocalisation decreases > Al has higher mp than Mg

Question 3

melting point of Si

Answer 3

Si has a giant molecular structure, large amount of energy is needed to break the strong covalent bonds between Si atoms

Question 4

melting points of P, S and Cl

Answer 4

P, S and Cl have simple molecular structures held together by weak id-id forces
S>P>Cl as no. of electrons decrease > strength of id-id forces decrease > amt of energy needed to overcome forces of attraction decrease > mp decrease