In the "Stick + H" view, hydrogen atoms are shown as white caps. Blue-and-white spirals show the hydrogen bonds they're involved in. Many of the hydrogens shown in this view are non-polar, meaning they won't participate in hydrogen bonds.
Light atom refers to hydrogen. Anything else is a heavy atom.
Foldit normally shows only heavy atoms. Certain View Options can reveal hydrogens as well:
- stick + H
- stick + polar H
- line + H
- line + polar H
In these options, the "+ H" version reveals all hydrogens, and the "+ polar H" option reveals only polar hydrogens, which can be involved in forming hydrogen bonds.
With these options, hydrogens are shown in white, using CPK coloring.