Question

Question 9
The ion of an element has 3 positive charges. 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 answer is (b).
Given that, charge = + 3,
mass number = 27 and number of neutrons = 14
Number of protons = atomic number
Atomic number = mass number - number of neutrons = 27-14 = 13
This is the atomic number of aluminium.
Therefore, this element is aluminium (Al).
Number of electrons in the Al atom = 13 Number of electrons in the $A{l}^{3+}ion=13-3=10$. As it is formed from the neutral atom by a loss of 3 electrons.