Which of the following has eight valence electrons? Ti4+ Kr Cl- Na+ all of the above
The Correct Answer and Explanation is:
Correct Answer: All of the above
Explanation:
To determine which of the listed species has eight valence electrons, we must consider the electron configuration of each atom or ion. An atom or ion with a full outer shell of eight electrons is said to have achieved a stable noble gas configuration, which is also known as the octet rule.
- Ti⁴⁺ (Titanium ion with a +4 charge):
- Titanium has an atomic number of 22.
- Neutral titanium has the electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s².
- Losing four electrons (to become Ti⁴⁺) removes the 4s² and 3d² electrons.
- Ti⁴⁺ becomes: 1s² 2s² 2p⁶ 3s² 3p⁶ → this is the same configuration as argon (Ar).
- Argon has eight electrons in its outermost shell.
- So Ti⁴⁺ has eight valence electrons.
- Kr (Krypton):
- Krypton is a noble gas with atomic number 36.
- Its full configuration ends in: 4s² 3d¹⁰ 4p⁶.
- The outermost shell (n = 4) has 2 (from 4s) + 6 (from 4p) = 8 valence electrons.
- So Kr has eight valence electrons.
- Cl⁻ (Chloride ion):
- Chlorine has an atomic number of 17: 1s² 2s² 2p⁶ 3s² 3p⁵.
- When it gains one electron to become Cl⁻, the configuration becomes: 3s² 3p⁶.
- The outer shell now has 2 + 6 = 8 valence electrons.
- So Cl⁻ has eight valence electrons.
- Na⁺ (Sodium ion):
- Sodium has an atomic number of 11.
- Neutral sodium: 1s² 2s² 2p⁶ 3s¹.
- Na⁺ loses the one 3s electron, leaving: 1s² 2s² 2p⁶ → same as neon (Ne).
- That is 8 valence electrons in the second shell.
- So Na⁺ has eight valence electrons.
Conclusion: All of the listed atoms or ions have eight valence electrons, which makes “All of the above” the correct choice.
