Rutherford used gold for his scattering experiment because gold is the most malleable metal and he wanted the thinnest layer as possible. The goldsheet used was around 1000 atoms thick. Therefore, Rutherford selected a Gold foil in his alpha scatttering experiment.
A=mass number (protons + neutrons)
Z=atomic number (protons)
N=number of neutrons.
A=Z+N
Data:
A=24
N=13
Therefore:
24=Z+13
Z=24-13=11
Answer: The atomic number of this atom is 11. (The element is sodium)