Question

How many grams does an atom of hydrogen weigh?

Answer 1

To answer this question, you must recall the Avogadro’s number. We know the molar mass of a hydrogen atom. Using the molar mass and Avogadro’ number we can find the mass of the atoms present in one mole of the substance. From this, we can easily find the weight of one atom of hydrogen atom.
Formula used: $n = \dfrac{w}{M}$
Where, $n$ represents the number of moles of the given substance
$w$ represents the given mass of the substance
And, $M$ represents the molar mass of the given substance.

Complete step by step solution
We know that the number of atoms or molecules present in one mole of a substance is always the same for all substances and is given by Avogadro's number. The Avogadro’s number is $6.022 \times {10^{23}}$ .
However the mass of one mole of the substance varies and is known as the molar mass. For hydrogen, the molar mass is $1{\text{ g/ mol}}$ .
From the mole concept, we now know that 1 mole of hydrogen contains $6.022 \times {10^{23}}$ atoms.
We can also say that $1{\text{ g/ mol}}$ of hydrogen contains $6.022 \times {10^{23}}$ atoms. The same can also be written as
$6.022 \times {10^{23}}$ atoms of hydrogen weigh $1{\text{g}}$ . So we can now calculate the mass of one hydrogen atom as,
${\text{mas}}{{\text{s}}_{{\text{H atom}}}} = \dfrac{1}{{6.022 \times {{10}^{23}}}}g$
$\Rightarrow {\text{mas}}{{\text{s}}_{{\text{H atom}}}} = 1.66 \times {10^{ - 24}}g$
So, the mass of one atom of hydrogen is $1.66 \times {10^{ - 24}}g$ which is also equal to 1 atomic mass unit.

Note:
It must be noted that the molar mass of hydrogen molecules will be different from the molar mass of hydrogen atoms. In the question, we use the molar mass of a hydrogen atom since we are supposed to find the weight of one atom.