Their locations can vary depending on the molecule they are associated with but they are usually in a "cloud " that is on the outside of an atom/molecule and if the atom is unstable the electrons tend to be located farther away from the atom.
Well, a magnet could DEFINITELY change if it gets exposed to heat, because you could melt the metal and change its shape.
If you hit it hard though, it wouldn't make much of a difference because the magnet is metal, so you'll probably just chip it or leave a dent.
Hope this helps ;)
M and S cuz they are in the same period