Having more than one atom in its molecule doesn't make
a substance a compound. It's only a compound if it has
atoms of different elements in its molecule.
Both atoms in an Oxygen molecule are the same element ... Oxygen.
Newton's first law of motion says something like "An object remains
in constant, uniform motion until acted on by an external force".
Constant uniform motion means no change in speed or direction.
If an object changes from rest to motion, that's definitely a change
of speed. So it doesn't remain in the state of constant uniform
motion (none) that it had when it was at rest, and that tells us
that an external force must have acted on it.
You look up the element in the periodic table. Subtract the atomic number (small number) from the mass number (big number). The answer is the number of neutrons.
A dwarf planet is a small celestial body resembling a planet, but lacks necessary things to be a planet
