We know that atoms are the building blocks of chemistry. Generally, the atomic number helps to differentiate one element from the other element and is defined by the number of protons present in it. Also, the mass number of any element is computed by adding the number of protons and neutrons. The mass number and atomic number are always represented in the whole number, as it is obtained by calculating the whole objects such as protons, neutrons and electrons.
Therefore, the mass number (A) is defined as the sum of the number of protons and neutrons present in the nucleus.
I.e., Mass Number (A) = Number of neutrons (n) + Number of protons (p).
A= n + p
p = A − n …(1)
From the given question, it is clear that
Atomic mass number = 13
Neutrons = 7
Now, substitute the values in (1), and we get
P = 13 - 7 = 6
Hence, the number of protons is 6.
It is known that,
Number of protons = Number of electrons = Atomic number
Therefore, the atomic number of the atom is 6.