Q25 / 150 · MHT CET 2024 (03 May Shift 1) · Chemistry
What is the representation of an element having mass number of 40 and 21 neutrons in it?
- A${ }_{18}^{40} \mathrm{X}$
- Correct answerB${ }_{19}^{40} \mathrm{X}$
- C${ }_{12}^{40} \mathrm{X}$
- D${ }_{20}^{40} \mathrm{X}$
Solution
3. Protons $(Z)$ : The number of protons can be determined by subtracting the number of neutrons from the mass number:
$Z=A-N=40-21=19$
So, the element has 19 protons. 4. Element symbol: The element with 19 protons is potassium (K), which has the atomic number 19.
Thus, the correct representation of the element is K-40 or ${ }_{19}^{40} \mathrm{~K}$.
Therefore, the correct answer is: (B) ${ }_{19}^{40} \mathrm{X}$.
So, the element has 19 protons. 4. Element symbol: The element with 19 protons is potassium (K), which has the atomic number 19.
Thus, the correct representation of the element is K-40 or ${ }_{19}^{40} \mathrm{~K}$.
Therefore, the correct answer is: (B) ${ }_{19}^{40} \mathrm{X}$.
Hence, the correct answer is option: 'B'.