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NEET Chemistry QUESTION #7413
Question 1
\(\text{Be}^{2+}\) is isoelectronic with which of the following ions?
  • \(\text{H}^+\)
  • \(\text{Li}^+\)✔️
  • \(\text{Na}^+\)
  • \(\text{Mg}^{2+}\)
Correct Answer Explanation
Be (Z=4): Be²⁺ has \(4-2=2\) electrons.

Checking options:
  • H⁺ (Z=1): 0 electrons
  • Li⁺ (Z=3): 2 electrons ✓ — isoelectronic with Be²⁺
  • Na⁺ (Z=11): 10 electrons
  • Mg²⁺ (Z=12): 10 electrons
Be²⁺ and Li⁺ both have 2 electrons (helium configuration).