Question

How do I determine the mass of one atom of an element?

Answer 1

One mole of any substance contains $6.023 \times {10^{23}}$ number of particles, in which the particles may be ions or atoms or molecules. From the molar mass of an atom and the above number which can be known as Avogadro’s number, the mass of one atom of an element can be determined.

Complete answer:
Chemical elements are the purest form of atoms. Atoms are the tiny particles that consist of subatomic particles and are invisible to the human eye.
To determine the mass of one atom of an element, we need molar mass of the atom. Generally, molar mass will be taken in gram per mole. Where one mole contains $6.023 \times {10^{23}}$ number of particles, in which the particles may be ions or atoms or molecules. The molar mass will be obtained from the periodic table which is given by the sum of the number of protons and number of neutrons.
To obtain the mass of one atom of an element, the molar mass should divide with the number of atoms in one mole.
Let us consider a chlorine atom which has molar mass of $35.5gmo{l^{ - 1}}$ and one mole of chlorine atom consists of $6.023 \times {10^{23}}$ number of atoms. Thus, one mole of chlorine atom in an element will be $\dfrac{{35.5}}{{6.023 \times {{10}^{23}}}} = 0.59 \times {10^{ - 22}}g{\left( {atom} \right)^{ - 1}}$
Thus, the mass of one chlorine atom is $0.59 \times {10^{ - 22}}g$

Note:
Avogadro’s number is the number that represents the number of atoms or ions or molecules present in one mole. To convert the number of atoms into moles, this number is very useful. The molar mass is in grams per mole and Avogadro’s number represents atoms per mole. Thus, moles in the fraction were cancelled and grams per atom remained.