How many atoms in 12.5 grams of sodium?
22.99 mol in one gram of sodium, so: 12.5/22.99=0.543714659 mol.
Round it to whatever you need to.
mol of Na = \(\frac{Mass of Na}{Molar Mass of Na}\)
= \(\frac{12.5g}{23.00g/mol}\)
= 0.54 mol
# atoms of Na = mol × avogadro's constant
= 0.54 mol × [6.02 × 10²³]
= 3.25 × 10²³