Answer :
you must perform stoichiometry! always divide by what you already have (this will make since in a moment)
5.2g Carbon | 1 mole/12.01g/mole | 6.02 x 10^23 atoms/1 mole | = atoms in Carbon
above is the basic stoichiometry set up but your calculation should be (5.2g/12.01g) x (6.02 x 10^23) = 2.61 x 10^23 atoms
5.2g Carbon | 1 mole/12.01g/mole | 6.02 x 10^23 atoms/1 mole | = atoms in Carbon
above is the basic stoichiometry set up but your calculation should be (5.2g/12.01g) x (6.02 x 10^23) = 2.61 x 10^23 atoms