Related Clues:

• __ bomb
• Hard thing to split
• Elemental bit
• Splitting it releases energy
• Excitable one
• Mr. ___, radioactive enemy of Captain Marvel
• Matter constituent
• Concern for Edward Teller
• Molecular bit
• Elementary bit
• One of three for H20
• Wee particle
• Neutron's home
• Molecule
• Bit with a nucleus