Explain why the melting point are different?

Answer 1

As heat fusion are different for different for substances, so the melting points.
Not only is heat required to raise the temperature of the solid to the melting point, but the melting itself requires heat called the heat of fusion.
The enthalpy of fusion (symbol: ΔfusH), also known as the heat of fusion, is the amount of thermal energy which must be absorbed or evolved for 1 mole of a substance to change states from a solid to a liquid or vice versa. It is also called the latent heat of fusion or the enthalpy change of fusion, and the temperature at which it occurs is called the melting point.

Answer 2

melting points are determined by the strength of intermolecular forces, which can vary a lot for different compounds. for instance ionic compounds have higher melting points than covalent compounds, because they are held together by electrostatic forces rather than dispersion forces.

the answer below is talking about covalent bonds which are *intra*molecular forces and have no effect on melting points. melting doesn't involve breaking molecules apart - it involves physically separating them. covalent molecules are electrically neutral and are attracted to each other only because charge will not be perfectly evenly distributed, so there will be a net attraction, but of a far smaller magnitude than for (charged) ions.

Answer 3

covalent bonds are held together because the have to share an electron to full the outer shell, this makes them stable (i.e if one molecule has 1 in its outer shell and has has 7 then they will share) they electrons are small and quite tightly packed, they have a weaker bond holding them together that takes less (thermal) energy to break,

ioninc bonds are held together by a magnetic force which is stronger