Change set

Pick exam & year, then Go.

Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q12 (NDA-I/2022) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Atomic and nuclear physics Answer Verified

The mass number of argon is 40. Which one of the following statements is correct?

Result
Your answer: —  Â·  Correct: C
Explanation

Argon (Ar) is a noble gas with an atomic number of 18. The atomic number represents the number of protons in the nucleus of an atom [1]. In a neutral atom, the number of electrons is equal to the number of protons to maintain electrical neutrality [1]. Therefore, an argon atom contains 18 protons and 18 electrons. The mass number is defined as the sum of protons and neutrons [1]. Given a mass number of 40 for argon, the number of neutrons is calculated as 40 minus 18, which equals 22 neutrons. Consequently, statement 1 is incorrect (18 protons, not 22), statement 2 is incorrect (22 neutrons, not 18), and statement 4 is incorrect (sum of protons and electrons is 36, not 40). Statement 3 is correct as argon has 18 electrons.

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.
100%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

CDS-I · 2017 · Q16 Relevance score: 3.47

There are two elements—calcium (atomic number 20) and argon (atomic number 18). The mass number of both the elements is 40. They are therefore known as

NDA-II · 2015 · Q65 Relevance score: 3.12

Which one of the following statements is correct?

CDS-I · 2018 · Q31 Relevance score: 2.89

Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?

NDA-I · 2025 · Q72 Relevance score: 2.88

Which one of the following statements is correct?

CDS-I · 2016 · Q44 Relevance score: 2.69

Which one of the following statements is not correct?