Some problems received some generous partial credit even though people ignored what the question was asking. If a problem asks for an explanation or discussion based on a previous answer, then discuss things in terms of the previous answer. In general, think comparisions. You find Zeff for Na to be about 1. What to say about that? A good idea would be to compare it to Z for Sodium. Saying it is small or big is not useful without a comparison. Again, we had a problem looking at finding the dissociation energy for HBr using a purely ionic model. Many people concluded it was covalent, but didn't use any of the information in the problem.