Related Clues:

• Split bit
• Tiny power source
• Elemental unit
• Symbol of the post-1945 age
• Chemistry bit
• Very tiny
• Film director Egoyan
• With 28-Across, particle accelerators
• Elemental building block
• Mighty bit
• Spray paint, e.g.
• Like some energy
• "I, __"
• Where electrons orbit
• ''Lost in Space'' figure