Question

What is meant by
A.Atomic number of an element.
B.Mass number of an element.
Explain with the help of an example.

Answer 1

Hint: We know that in order to answer this question, one must have a clear idea about the structure of the atom and the various parameters related to it. An atom of any element has a fixed atomic number and mass number.

Complete answer:
 An element can also have various isotopes and isobars (compared to the other species).
Atomic number: The atomic number is the total number of protons present in the atom. For example, the total no. of protons in a carbon atom is \[6\], so its atomic no. is \[6.\] Also, one atom of \[Na\] contains \[11\] protons and \[12\] neutrons, so its mass no. is \[23.\]
Mass number: It is the sum of the number of neutrons and the number of protons. For example, the atomic number of Lithium is \[4\] which is equal to the number of protons; the number of neutrons of magnesium is \[4.\] The mass number is equal to \[8\left( 4+4 \right).\]

Additional Information: Atomic number and mass number both are main characteristics of an atom of the element. If you know the atomic and mass number of an atom of the element, then you can easily calculate the number of neutrons present in the nucleus of the atom. Neutral atom consists of the same number of protons and electrons. By knowing atomic number and mass number of an element we can predict many properties of the element.


Note:
Remember that Mass number is the number of nucleons, i.e., number of protons and neutrons. When two different elements have the same mass number, they are called isobars. When two atoms have the same atomic number but the different mass numbers, they are called isotopes of each other.