What is the unit of measurement used for atomic particles?

That's going to depend on exactly what you want to measure about the particles. If it's the particle's mass then the unit is related to the kilogram. If your measuring the size of the particle then you will use a unit related to the meter. If you want to measure the age of the particle then you'll use a unit related to the second.

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.