Related Clues:

• See 15-Across
• Charged atom
• Elementary particle
• Physicist's study
• 'Am ___ time?'
• + or - item
• Negatively charged particle
• It may have an extra electron
• Physics subject
• See 41-Down
• Hydrolysis atom
• A hydrogen atom has one
• Ca++ or Cl-, e.g.
• Element element
• Euripides play