Alpha particle is composed of 2 neutrons and 2 protons (compared to as ahalium nucleus)
hope that helps
To get the number of gold atoms, you have to divide the mass of the gold by the mass of the gold atom. It follows this simple equation

.
Let x be the number of gold atoms. Plug in the values to a calculator.
x =

Both have the same units so the unit gram(g) can be cancelled.
x then would be equal to 1.53x10^22. So there are 1.53x10^22 atoms of gold in 5 g of gold