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Sodium (Group 1) is highly reactive, while Neon (Group 18) is unreactive. Explain why this is true based on their valence electrons.

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Answered by GPT-5 mini AI
The chemical reactivity of an element is largely determined by how easily it can change its valence‑electron arrangement to reach a stable electron configuration.

- Sodium (Group 1): electronic configuration 1s2 2s2 2p6 3s1 — it has a single valence electron (3s1). Losing that one electron gives the noble‑gas configuration of neon (a full octet): Na → Na+ + e−. Because removing that outer electron costs relatively little energy (low first ionization energy), sodium readily loses it and so is highly reactive (especially with nonmetals like chlorine or oxygen).

- Neon (Group 18): electronic configuration 1s2 2s2 2p6 — its outer shell is already full (an octet). That is a very stable arrangement, so neon has little tendency to lose or gain electrons. Removing an electron requires a large amount of energy (very high ionization energy) and adding an electron is energetically unfavorable. As a result, neon is chemically unreactive under normal conditions.

In short: sodium is reactive because it can easily achieve a stable, full shell by losing one valence electron; neon is unreactive because its valence shell is already full and stable.