How many grams of potassium chloride is produced if 6.78 mols of potassium reacts?

Potassium   react  with  chlorine  to  form  potassium  chloride
2K +  Cl2  ---> 2 KCl
The  reacting  ratio  of   potassium  reacted  and  KCl  produced  is  1:1
by  use  of  this  ratio  the number  of  moles  of  KCl  produced  is  therefore =6.78moles
mass =molar  mass  x  number of  moles
molar  mass  of  KCl=74.5  g/moles
mass  is  therefore=  74.5 x  6.78moles=505.11g

The correct answer should be "electrons orbit the nucleus in circular motions exactly as shown on the classic bohr model."