Well first of all, when it comes to orbits of the planets around
the sun, there's no such thing as "orbital paths", in the sense
of definite ("quantized") distances that the planets can occupy
but not in between. That's the case with the electrons in an atom,
but a planet's orbit can be any old distance from the sun at all.
If Mercury, or any planet, were somehow moved to an orbit closer
to the sun, then ...
-- its speed in orbit would be greater,
-- the distance around its orbit would be shorter,
-- its orbital period ("year") would be shorter,
-- the temperature everywhere on its surface would be higher,
-- if it has an atmosphere now, then its atmosphere would become
less dense, and might soon disappear entirely,
-- the intensity of x-rays, charged particles, and other forms of
solar radiation arriving at its surface would be greater.
