The electron dot diagram tells
us about how many electrons are being shared between atoms. Also, the number of
valence electron to be shared corresponds to the group number the element
belongs. Say for example H2O, hydrogen has one valence electron and oxygen has
two valence electrons.
It takes more energy to rip apart stronger bonds (that's mostly just common sense there). The boiling point increases because it would take more energy to get the molecules to go from a stuck together liquid, to separating in a gaseous form.
