Which element has the highest first ionisation energy?
Answer and explanation
Correct answer: A. Helium
Helium holds its two electrons close to a nucleus with no inner shielding, giving the highest ionisation energy.
Answer: Helium.
Why not the others: Lithium: it has a very low ionisation energy. Sodium: it has a low ionisation energy. Neon: it is high, but less than helium.
Answer: Helium.
Why not the others: Lithium: it has a very low ionisation energy. Sodium: it has a low ionisation energy. Neon: it is high, but less than helium.
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