I tutor general chemistry at both the high school and college level. Below is a list of topics that are often omitted to the detriment of the students.

As a tutor, I have the opportunity to see the curricula of many schools and their deficiencies. Here are some worrying omissions that I've observed:

Scientific notation and significant figures are not stressed.

Dimensional analysis it's not emphasized to the degree that it should be. This is massively important!

The influence of electronegativity difference on bond dipole moment.   How this and molecular geometry affect trends in boiling point and melting point.

This is not an exhaustive list by any means.

Your thoughts?