Question

For $Al$ , its atomic number is $13$ and its mass number is $27$ . How many neutrons does it have?

Answer 1

We must need to know that the weight of a given atom depends on the number of protons and the number of neutrons. The identity of an atom is determined from the number of protons. The number of protons or electrons in an atom is equal to the atomic number of an element. We know that the number of protons and neutrons are the fundamental particles which determine the mass of a given isotope.

Complete step by step answer:
The Atomic number of aluminium is $13$ .
The mass number of aluminium is $27$
We know that the atomic number is equal to the number of electrons; the number of electrons present in aluminum is $13$
One can calculate the number of neutrons as follows,
The number of neutrons present in Aluminum is $= 27 - 13 = 14$

Additional information:
We need to know that the electronic configuration of aluminium is $\left[ {Ne} \right]3{s^2}3{p^1}$.
The most stable and common isotope of aluminium is ${_{13}^{27}}Al$. The radioactive isotope of aluminum is ${_{13}^{26}}Al$ and this isotope is used in radio dating.
Among boron family aluminium is a weak metal and the oxidation state of aluminium is $+ 3.$
The electronegative value of aluminium is $1.61$.
Aluminum looks like silver, both in shading and in extraordinary capacity to mirror light. Aluminum is delicate, non-attractive and flexible.

Note: We must remember that the electrons are the other fundamental particle of an atom and the rest mass of electrons is very small when compared with that of the nuclear particles. On the other hand the number of electrons gained or lost by an atom by reaction with other substances decides the chemical reactivity of the species.