What does the big ‘2’ in 2NH3 mean?

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

Identify and describe the three ways that mutations affect organisms.

Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom? some uncharged particles are scattered by a gold foil. all uncharged particles are attracted towards a gold foil. all positively charged particles pass straight through a gold foil. some positively charged particles bounce back from a gold foil.