Why would alpha particles pass through the atom in Thompson’s plum-pudding model Can someone show me the calculation (along with the data) as to why the alpha particles will pass through the atom in Thompson’s Plum pudding model?
 A: I do not think one needs calculations:

According to the plum pudding model, there were negatively charged particles i.e. electrons embedded or suspended in a sphere of positive charge (electrons presented as plums inside the bowl of pudding)


The plumb pudding on the left, assumes that the neutrality of the atoms is due to the mixing of positive and negative charges, as in the image. On the right the Rutherford experiment showed that the positive charges were concentrated in the center, leaving the negative on the periphery.

After performing his experiment he made observations:
.    Almost all the alpha particles did pass through the foil but
.    Some alpha particles were deflected off at different angles as observed at the screen of the detector.
.    Very few of the alpha particles (one or two) even bounced backwards after hitting the gold foil.
On the basis of these observations Rutherford made the following conclusions:
.    Since most of the alpha particles passed straight through the gold foil without any deflection, most of the space within the atoms is empty.
.    Since some of the alpha particles (which are big in size) were deflected by large angles or bounced backwards, they must have approached some positively charged region responsible for the deflection. This positively charged region is now called the nucleus.
.    As very few alpha particles undergone the deflection, it was concluded that the volume occupied by the central region ( nucleus ) is very small.
.    Since alpha particles which are relatively denser, were deflected by the central volume of charge, it shows that almost the complete mass of the atom must be within the central volume.

