Related Clues:

• Looking back, it's about most unfinished chemistry at the centre of a couple of compounds
• More is needed to synthesise an atomic nucleus
• Atomic nucleus; is more (anag.)
• Atomic nucleus with a different energy state to other nuclei
• A few locked in centre of firm's compound
• Leader of infamous county set's abandoned compound
• Beta carotene, e.g
• Methylpropane, vis-à-vis butane
• Beta carotene, to carotene
• Octane, e.g
• Multiple-formed compound
• One of two or more chemical compounds with the same formula but different atomic arrangements
• Fructose, to glucose
• Chemical variation
• Compound with same formula as another but not atom arrangement