Question

How many protons, neutrons and electrons does a magnesium atom with a mass number of 25 contain?

Answer 1

Hint: The answer here is based on the basic concept of chemistry which makes use of formula to find the number of protons, neutrons and electrons which is based on the periodic table and is given by, number of protons = mass number – number of neutrons neutrons.

Complete step by step answer:
- We are familiar with the concepts of atoms, their structure, composition and also the properties about it from the basic concepts of chemistry.
Let us now refresh those concepts so that we can deduce the correct answer.
- An atom is the smallest particle that can exist which builds the entire universe. It is composed of a central nucleus which has positively charged species called protons and the neutral species called neutrons.
- The electrons that are negatively charged are revolving around the orbit of the nucleus.
- The protons are nothing but the one which gives the atomic number and always the number of protons are equal to the number of electrons and therefore they are equal.
- Neutrons and protons together make up the mass of an element and these neutrons present can be calculated using the mass number which is given by the formula, number of protons = mass number – number of neutrons neutrons.
- Therefore, the atomic number of magnesium atoms is 12 and thus the number of protons in this element is 12 which in turn equals the number of electrons.
- Now, according to the formula, the number of neutrons present is calculated as,
Number of neutrons = mass number – number of protons $\Rightarrow n_n=25-12=13$
Thus, this is the required answer.

Note: Note that the atomic number of an element is constant and does not change but the mass number of an element can change with the same atomic number and they are called as the isotopes of that element.