Alpha particles are relatively heave and can be stopped by a sheet of paper.
What part of it are you confused about
Answer: The suffixes of the names of polyatomic ions have a pattern associated with them. ... For example, the sulfite ion has three oxygen atoms whereas the sulfate ion has four oxygen atoms.
1 mole Hg --------------- 6.02x10²³ atoms
?? moles Hg ------------ 1.30x10⁷ atoms
(1.30x10⁷) x 1 / 6.02x10²³ => 2.159x10⁻¹⁷ moles
