Final answer:
The force exerted by the floor that opposes an object's weight is a normal force. It is the surface pushing perpendicular and away from itself to support objects against gravity. The force that holds an atom together is the electric force, not the normal force.
Step-by-step explanation:
The force of the floor pushing up on you to counter your weight is an example of a normal force. A normal force is a contact force that surfaces exert to support the objects resting upon them, and it acts perpendicular to and away from the surface. This force balances the weight of the object due to gravity, maintaining a state of equilibrium when the object is stationary.
Regarding true or false questions, it is false that the normal reaction is the force that opposes the force of gravity and acts in the direction of the force of gravity. Instead, the normal force actually acts in the opposite direction to the force of gravity.
The force responsible for holding an atom together is electric, as it governs the attraction between the positively charged nucleus and the negatively charged electrons.