Question

Atomic number of aluminium is 13 and mass number is 27. Calculate number of electrons, protons and neutrons in the ion formed. Represent the ion. What will be its valency?

Answer 1

Hint: As we know that protons are positively charged, electrons are negatively charged. We can find protons, electrons and neutrons easily. To find the number of neutrons, subtract the atomic number from the mass number. If the given atom is neutral, the number of electrons will be equal to the number of protons.

Complete Solution :
As we know, the mass number of an atom tells us about the total number of protons and neutrons present in the nucleus of an atom.
- As we are discussing the isotope of aluminium, it tells us that this atom will have an exact number of protons in the nucleus.
- As we know that atomic number shows the number of protons that an atom has in its nucleus. As we are provided with the information that Atomic number of aluminium is 13. Which clearly means that any atom, which is an isotope of aluminium will have 13 protons in the nucleus.
- The number of electrons surrounding the nucleus will be equal to the proton number. Hence, there will be 13 electrons. Now, we will calculate the neutrons present as:
Mass number = no. of protons + no. of neutrons.
So, the no. of neutrons = 27 - 13 = 14.

- After ion is formed,
$$Al\to A{l}^{3+}+3e^{-}$$
The number of electrons are= 13 - 3 = 10
Here, the number of protons are 13
And neutrons are=27 - 13 = 14.
the ion can be represented as: $A{l}^{3+}$ .It has the valency of +3
Hence, we can conclude that number of electrons, protons and neutrons in the ion formed is 10, 13, 14 .The ion can be represented as: $A{l}^{3+}$ and its valency is +3.

Note: - We should note that the mass number of any atom is equal to the sum of the neutrons and protons in the nucleus.
- The total number of neutrons is equal to the difference between the mass number and atomic number of an atom.