Question

The ion of an element has $3$ positive charges. The mass number of the atom is $27$ and the number of neutrons is $14$. What is the number of electrons in the ion?

• A. $13$
• B. $10$
• C. $14$
• D. $16$

Answer 1

The correct option is B

$10$

Explanation for correct option

(B)$10$

Step1. Formula for mass number

$\text{Mass number=Number of protons+Number of neutrons}$

Step2. Calculation of number of protons

$$\begin{gathered} \text{Mass number=Number of protons+Number of neutrons} \\ 27=\mathrm{Number}\mathrm{of}\mathrm{protons}+14 \\ \mathrm{Number}\mathrm{of}\mathrm{protons}=13 \end{gathered}$$

Step3. Number of electrons in the ion

• The number of protons is equal to the number of electrons in an atom.
• So, the number of electrons in an atom is $13$.
• The ion of an element has $3$ positive charges. So, the number of electrons in the given ion is $13-3=10$.

The number of electrons in the ion is $10$.

Explanation for incorrect option

The number of electrons in the ion is $10$. Hence, options (A),(C), and (D) are incorrect.

Hence, option (B) is correct. The number of electrons in the ion is $10$.