Related Clues:

• Chemistry bit
• Film director Egoyan
• With 28-Across, particle accelerators
• Elemental building block
• Mighty bit
• Where electrons orbit
• Electron's locale
• Building block of matter
• Bit that may be split
• Molecule maker
• Fissionable unit
• Something smashable
• Basic unit
• Director Egoyan
• Physicist's bit