Question

\(Be^{2+}\) is isoelectronic with which of the following ions?

• A. \(Li^+\)
• B. \(Na^+\)
• C. \(Mg^{2+}\)
• D. \(H^+\)

Answer 1

The Correct Option is A

To determine which ion is isoelectronic with \(Be^{2+}\), we must first understand the concept of being isoelectronic. Isoelectronic ions or atoms have the same number of electrons.

Let's analyze the electron configurations and the number of electrons for each option:

1. \(Be^{2+}\):

   The atomic number of beryllium (Be) is 4. Normally, a neutral Be atom has 4 electrons. The ion \(Be^{2+}\) means it has lost 2 electrons, so it now has 2 electrons left.

2. \(Li^+\):

   The atomic number of lithium (Li) is 3. A neutral Li atom has 3 electrons. The ion \(Li^+\) means it has lost 1 electron, so it now has 2 electrons left. Therefore, \(Li^+\) is isoelectronic with \(Be^{2+}\).

3. \(Na^+\):

   The atomic number of sodium (Na) is 11. A neutral Na atom has 11 electrons. The ion \(Na^+\) has lost 1 electron, so it now has 10 electrons left, which is not isoelectronic with \(Be^{2+}\).

4. \(Mg^{2+}\):

   The atomic number of magnesium (Mg) is 12. A neutral Mg atom has 12 electrons. The ion \(Mg^{2+}\) has lost 2 electrons, so it now has 10 electrons left, which is not isoelectronic with \(Be^{2+}\).

5. \(H^+\):

   Hydrogen (H) with an atomic number of 1, in its neutral state has 1 electron. The ion \(H^+\) has lost its only electron and now has no electrons, which again is not isoelectronic with \(Be^{2+}\).

Conclusion: Based on the analysis, \(Li^+\) is the ion isoelectronic with \(Be^{2+}\) as both have 2 electrons.