Related Clues:
- Primary: Abbr.
- Earth, wind or fire, to an early scientist
- Na, Ne, Ni or No
- Natural environment
- Periodic-table component
- B or C, but not A or D: Abbr.
- Silver or sulfur
- Grades K-6, perh.
- Gold or silver, but not bronze
- Helium or hydrogen
- School for 7-year-olds, briefly
- Gold, e.g.
- Part of 51-Across: Abbr.
- Si or No, e.g.
- Ca, Co or Cu