When a gold sheet is bombarded by a beam of α-particles, only a few of them get deflected whereas most go straight, undeflected. This is because :

The force of attraction exerted on the $\mathrm{\alpha }$-particle by the oppositely charged electrons is not sufficient.

A nucleus has a much smaller volume than that of atom

The force of repulsion acting on the fast moving $\mathrm{\alpha }$-particles is very small.

The neutrons in the nucleus do not have any effect on the $\mathrm{\alpha }$-particles.