Calculate the number of atoms in 2.0g of hydrogen atoms?

First you calculate how many moles there are in 2.0 grams of hydrogen (H2) atoms.
Hydrogen has a relative atomic mass (RAM) of 1 g/mol, but there are 2 hydrogen atoms: 1 x 2 = 2 g/mol

To work out how many moles there are,
use the formula: n(moles) = mass ÷ molar mass
n(moles) = 2 grams ÷ 2 g/mol = 1 mol

Then use Avogadro's Constant : 6.023 x 10^23
= 1 x 6.023 x 10^23
= 6.023 x 10^23

Final step is to multiply it by the number of atoms, in this case there are 2.
= 6.023 x 10^23 x 2
= 12.046 x 10^23
= 1.205 x 10^24

that ^ should be your final answer

have a great day :)