A neon atom (Ne) is unreactive for which of the following reasons?

• A. It has 7 valence electrons.
• B. It has 8 valence electrons.
• C. Its valence shell is full of electrons.
• D. It has 20 valence electrons.
• E. b and c only.

Answer: (E)

Verified step by step guidance

1. Identify the atomic number of neon from the periodic table, which is 10. This indicates that a neutral neon atom has 10 electrons.
2. Determine the electron configuration of neon. The first two electrons fill the 1s orbital, and the next eight electrons fill the 2s and 2p orbitals, resulting in the configuration: 1s² 2s² 2p⁶.
3. Recognize that the outermost shell (valence shell) for neon is the second shell, which contains the 2s and 2p orbitals.
4. Calculate the number of valence electrons in neon. The 2s² 2p⁶ configuration shows that there are 8 electrons in the valence shell.
5. Conclude that neon is unreactive because its valence shell is full with 8 electrons, satisfying the octet rule, which makes it stable and unlikely to react with other elements.