What is the best explanation for why a particle is striking
point X?
This image shows a stream of positively charged particles
being directed at gold foil. The positively charged particles
are called "alpha particles and each one is like a nucleus
without any electrons.
Alpha particles are mostly empty space, so they move in
random directions, and one of these alpha particles can
strike point X
The gold atoms contain negative electrons, so when
alpha particles strike the gold they keep moving but in
various directions
If an alpha particle hits the gold foil, a gold nucleus splits
and a particle from it flies out at point X.
When the dense, positive alpha particle passes close to
a positive nucleus of gold, the alpha particle repels and
hits the screen at point X.