To determine the number of atoms in a given mass of an element, you need to use Avogadro's number and the molar mass of the element.
The molar mass of magnesium (Mg) is approximately 24.31 grams/mol.
First, calculate the number of moles of magnesium using the formula:
moles = mass / molar mass
moles = 20 g / 24.31 g/mol ≈ 0.82 mol
Next, use Avogadro's number, which is approximately 6.022 x 10^23 atoms/mol, to calculate the number of atoms:
number of atoms = moles * Avogadro's number
number of atoms = 0.82 mol * (6.022 x 10^23 atoms/mol) ≈ 4.944 x 10^23 atoms
Therefore, there are approximately 4.944 x 10^23 atoms in 20 grams of magnesium (Mg).