What is the mass of 5.3x10^9 atoms of Ne? Answer in grams.

You need the following information to solve this problem:
1. The molar mass of neon is 20.18 grams per mole. (From the Periodic Table.)
2. One mole of a substance contains 6.02 x 10^23 particles.
You can find the mass of a given number of neon atoms by multiplying it by conversion factors expressing the above relationships. The conversion factors we will use are:
1 mole/6.02 x 10^23 atoms
and
20.18 grams/1 mole
When the correct conversion factors are used all units cancel out except those that express the answer. In this case atoms and moles cancel out leaving units of grams:
(5. x10^9 atoms)(1 mole/6.02x10^23 atoms)(20.18 grams/1 mole)
= 1.8x10^-13 grams
Alternatively, you could break this down into two problems by finding the number of moles and then the mass:
(5.3x10^9 atoms)(1 mole/6.02x10^23 atoms) = 8.9 x 10^-15 moles
(8.9x10-^15 moles)(20.18 grams/mole) = 1.8x10^-13 grams
 
http://www.pathwaystochemistry.com/chemistry-qa/videos/conversion-factors-part-3-multistep-conversions/