Answer: Gas has loosely packed atoms, liquids have mediumly packed atoms, and solids have tightly packed atoms.
Explanation: Solids have tightly packed atoms which is what keeps them in their defined shape. They have a defined volume and a defined shape.
Liquids have mediumly packed atoms because liquids don't have a definite shape and take the shape of the container they are placed in. It has a definite volume, but an indefinite shape.
Gases have loosely packed atoms because gases can float around anywhere. They don't have a definite volume, and they don't have a definite shape.