Pluto
Pluto is the slowest planet to move around the sun, because of its far distance.
The speed of a planet revolving around the Sun is slowest at the aphelion, which is the point in its orbit farthest from the Sun.
Mercury is the fastest moving planet around the sun. It is second slowest to rotate about its axis, Venus being the slowest.
Neptune would move the slowest. The orbit speed is related to the distant the planets are to the sun. Farther the planet, slower the pace. Remember, Pluto is no longer a planet.
Sedna.
When it is farthest from the Sun. This point is known as aphelion. *Aphelion = Furthest point from the Sun.
mercury
Neptune. (Pluto is no longer considered a planet, but, rather, a dwarf planet.)
The farther a planet is from the sun, the slower it moves in its orbit. So the planet with the largest orbit is the slowest. That's Pluto ... if you still consider Pluto a planet ... or Neptune if you don't.
Curiously, the nearer the planet is to the Sun the faster it orbits. Thus Mercury orbits the fastest, whereas Neptune is the slowest.
The Planet Venus has the slowest rotation rate because one day there is longer than the year on Venus or longer than its revolution around the sun.
Mercury has the slowest revolution around the sun, taking about 88 Earth days to complete one orbit.