How many atoms are in 80.7 g of pure aluminum?

Like Roman said Avogadro's number is the key to your problem. The value that you'll use on paper is 6.022x10^23. Luckily in our case a mol specifically refers to the amount of atoms. Its a weird concept but 1.97 mol of Aluminum is the exact same amount of atoms as say helium. The only differences lay in the total mass of the sample.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).