How many molecules of carbon dioxide are in 243.6 g of carbon dioxide?

1) how many electrons are in each energy level of the following elements? a. he b. na c. na d. ne 2) how many valence electrons are percent in the following atoms? a. s b. mg c. be d. cl 3) which of the following elements are stable as atoms? a. he b. o c. cl d. ar if you are able to provide the work as to how you got the answers that would be greatly appreciated. : )

For ai it's atomic number is 13 and it's mass number is 27 how many neutrons does it have

What happened to the amount of carbon dioxide in the atmosphere from 2010–2017?