I've gone and added tons of categories and levels.

The categories added:

• All of a group: All of the alkali metals, alkaline metals, etc.
• All of a group - other: All of the solids, gases, liquids, etc.

The levels added:

• Groups: All of the groups have been added.
• Periods: All of the periods have been added.

That's all!

If none of it makes sense please feel free to complain. These are not the cleanest categories.