Which of the following will have highest melting point?
C
The melting and boiling points of group 14 elements are much higher than those of corresponding group 13 elements. This is because group 14 elements from four covalent bonds with each other; hence, there exist strong binding forces between their atoms in the solid as well as in the liquid states. The melting and boiling points decrease down the group (↓). This is due to corresponding decrease in the interatomic forces of attraction down the group (↓).
Therefore, C>B
B>Al
C>Ge
Therefore, carbon will have highest melting point. Its melting point is extremely high.