Question

Explain the following observations: Magnesium oxide (MgO) and sodium fluoride (NaF) have the same crystal lattice structure and approximately the same formula weight, but MgO is almost twice as hard as NaF. The melting points of MgO and NaF are 2852^oC and 993^oC, respectively. The boiling points of MgO and NaF are 3600^oC and 1695^oC, respectively.

Answer 1

1)

the first type of bonding are those INTERMOLECULAR bondings, that is, Mg-O and Na-F

the Na-F interaction is the strongest, sinc eit is pretty IONIC

the Mg-O is a pretty strong interaction ,therefore melting/boiling points are pretty high

2)

the second type of interaction is about INTRAMOLECULAR forces

which is the type of array the NaF and MgO will experience, this is about Crystal array and lattice forces

expect NaF to have a higher energy sinc eNa and F are extremly polar

the second type