Related Clues:

• Pentane, e.g.
• Compound variant
• U-235, e.g.
• Carbon-14, for one
• Compound's close relative
• Uranium-238, e.g.
• Atomic relative
• Compound related to another
• Carbon-13, e.g.
• Chemically related compound
• Compound variation
• Dating material?
• Compound similar to another
• Helium-3, e.g.
• Springfield minor leaguer