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
First step: convert 22.4% into fraction
that is 22.4/100 which is equivalent to 0.224
The mass of Cucl2 contained in 75.85 of 22.4% by mass of solution of CUcl2 in water is therefore,
0.224 x75.85=16.99g
alternatively
75.85 --->100%
? 22.4%
by cross multiplication =(22.4 x 75.85)/100 =16.99g
The answer is nucleation because can turn liquids into solids.