What is the mass, in grams, of a sample of 7.83 x 10^24 atoms of helium (he)? show your work or explain thr steps that you used to determine your answer.

An important information, specifically a constant, we need to know is the Avogadro's number. Avogadro's number is equal to 6.022*10^23 mol^-1. 
This is the constant we use to convert atoms to moles. So we need to divide 7.83 x 10^24 atoms with the Avogadro's number to get the number of moles. That will be equal to 13 moles of He. Then to convert  moles to grams we need the molar mass of Helium (4 grams/mole). We then multiply the number of moles with the molar mass of Helium. We would have 52 grams of Helium. 

There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.