Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q36 (NDA-I/2014) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Which of the following pairs represents isoelectronic ions?

Result
Your answer: —  Â·  Correct: D
Explanation

Isoelectronic species are defined as atoms, ions, or molecules that possess the same number of electrons and identical electronic configurations [1]. To identify the correct pair, we calculate the electron count for each ion. Calcium (Ca) has an atomic number of 20; losing two electrons to form Ca2+ results in 18 electrons. Sulfur (S) has an atomic number of 16; gaining two electrons to form S2- results in 18 electrons. Since both Ca2+ and S2- have 18 electrons, they are isoelectronic. Other options are incorrect: Na+ (10e-) and K+ (18e-) differ, as do Mg2+ (10e-) and Ca2+ (18e-). Potassium (K) as an atom has 19 electrons, while Mg2+ has 10, making them non-isoelectronic.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.3 HOW DO METALS AND NON-METALS REA ALS REACT? > p. 47
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
10%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

NDA-I · 2019 · Q14 Relevance score: 7.27

In which of the following pairs are the ions isoelectronic?

NDA-I · 2012 · Q20 Relevance score: 0.71

Which one among the following is correct regarding 20Ne, 23Na+, 19F- and 24Mg2+?

NDA-I · 2021 · Q47 Relevance score: -2.80

Which of the following sets of elements has the same valency?

NDA-I · 2012 · Q21 Relevance score: -2.84

Which of the following pairs is/are correctly matched? 1. Isotopes : Atoms with same atomic number but different atomic mass 2. Isobars : Atoms with same number of neutrons but different atomic number 3. Isotones : Atoms with same mass number but different atomic number Select the correct answer using the code given below : Code: