How many moles are 1.20x10^25 atoms of phosphorus. Look at the picture

19.9 moles

Explanation:

Each mole has 6.02 x 10^23 many atoms. This number is commonly known as "Avogadro's Number."

In this problem, we have 1.2 x 10^25 atoms of phosphorus.

Thus, (1.2 x 10^25)/(6.02 x 10^23) is the number of moles in 1.20 x 10^25 many atoms of phosphorus.

(1.2(10^25))/(6.02(10^23))

19.9 moles.

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.