Question

The ion of an element has 3 units positive charge. 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

Given, mass number = 27 and number of neutrons = 14
Mass number = Number of protons + Number of neutrons.
$\Rightarrow 27=$ Number of protons + 14

Number of protons $=27-14=13$

Now, we know that for a neutral atom,
Number of protons = Number of electrons
Given, that the ion has 3 units positive charge i.e. number of electrons is three less than the number of protons.

So, the number of electrons in the given element $=13-3$
$=10$