Question

What is atomic mass?

Answer 1

Hint: The nucleus is the solid mass present in center of the atom which consists of two types of particles , the positively charged particles called as protons and the neutral particles called as the neutrons and both are collectively responsible for the mass of the atom. Now you can easily answer the given statement.

Complete answer:
First of all, let’s discuss what an atom is. An atom is the smallest particle of an element. Two or more atoms combine to form molecules and molecules combine to form compounds and elements.
Now considering the statement as;
Each atom consists of a solid mass that is present in the center of the atom known as the nucleus of the atom.
Each nucleus within the atom consists of two types of particles; the positively charged particles i.e. the protons along with the neutral particles i.e. the neutrons which carry no charge. These both i.e. the protons and the neutrons are collectively responsible for the mass of the nucleus.
Outside the nucleus are present the negatively charged particles i.e. electrons which are revolving around the nucleus in fixed circular orbits.
The number of protons in the nucleus represents the atomic number which is denoted by Z and the total number of protons and the neutrons in the nucleus represents the mass number which is denoted by A.
So, thus, the atomic mass (A)= number of protons+number of neutrons.
Mathematically;
$A=P+N$ A

Note:
The number of electrons that are revolving around the nucleus and the number of protons which are present inside the nucleus are the same so that the atom as a whole is electrically neutral.