Question

What is the mass in $grams$ of a single atom of $chlorine$ ? (Atomic mass of $chlorine$= $35.5$)

Answer 1

To answer the above question we need to find the number of moles of the substance. Molecular mass is expressed in a unified atomic mass unit which is equal to the mass of that given compound in $1mole$ of the molecule.

Complete answer:
Molecular mass is given by dividing the mass of a sample compound by the amount of substance in that sample. It is the mass of $1mole$ of the substance or equals the Avogadro’s number which is $6.022 \times {10^{23}}$ particles expressed in grams.
Keeping this concept in mind we will solve the given question
Atomic mass of $chlorine$=$35.5$
This means that $6.022 \times {10^{23}}$ atoms of $chlorine$ have a mass of 35.5$$$$grams
This can be summed up as
1 mole = Atomic mass of $chlorine$= Avogadro’s number
1 mole $chlorine$= 35.5$$$$grams= $6.022 \times {10^{23}}$
For 1 $chlorine$ atom = $\dfrac{{35.5}}{{6.022 \times {{10}^{23}}}}$
$= 5.89 \times {10^{ - 23}}g/atom$
Thus the mass in $grams$ of a single atom of $chlorine$ $= 5.89 \times {10^{ - 23}}g/atom$

Additional information: The term molecular mass, molar mass and molecular weight are used interchangeably. The molecular mass is more commonly used when referring to the mass of a single or specific well defined molecule and less commonly than molecular weight when referring to a weighted average sample. The molecular mass of small to medium size molecules, measured by mass spectroscopy, can be used to determine the composition of elements in the molecules.

Note:
Another way of determining the molecular mass is by adding the atomic masses of all the compounds. This is done by calculating the molar mass of a compound with multiple atoms and summing up all the atomic mass of the constituent atoms.