Question

The atomic mass of potassium is 39. If its atomic number is 19, how many neutrons are in each potassium atom?

Answer 1

Hint: The answer here is based on the facts about the general concepts of chemistry which says that number of protons is equal to electrons and the number of neutrons can be determined using the formula,$n_n=m-n_p$

Complete answer:
In the lower classes of chemistry, we have studied about the concepts of general chemistry which deals with the fact about the structure of atom and its constituent parts that is nucleus
- Atoms are the smallest species about 100 picometers in size and are composed of protons that are positively charged and neutrons that are the neutral atoms and the electrons that are negatively charged revolve around it.
- Let us now calculate the number of neutrons present in the potassium as per the data given.
Potassium is having the atomic symbol$P$and according to the data given the atomic number is 19 and the mass number is 39.
We know that the number of protons is always equal to the number of electrons in any atom and also the total number of protons present is given by their atomic number.
Thus, the protons present in the atom is 19.
Now, by using the formula to calculate the number of neutrons in an atom that is,
$n_n=m-n_p$
where, m is the mass number of an element.
Substituting the values, we have
$$n_n=39-19=20$$
Therefore, total number of neutrons present in potassium element is 20

Note:
Note that the total number of protons and electrons can be found using the same formula because the total number of protons are always equal to the total number of electrons and the sum of protons and neutrons constitute the mass number of an element.