Question

which of these is true about atoms? scientists have never observed an atom, but they think they exist. atoms are too small to see with our eyes. only matter in the solid state has atoms. atoms are perfectly still when matter is in the solid state.

Explanation:

Atoms are extremely small particles. Their size is on the order of picometers (1 picometer = 10^(-12) meters). The human eye has a resolution limit that is much larger than the size of an atom. So, atoms cannot be seen with the naked eye.
Scientists have observed atoms using advanced microscopy techniques like scanning tunneling microscopy. Matter in all states (solid, liquid, gas) is made up of atoms. Atoms in solids are in constant motion (vibrational motion).

Answer:

Atoms are too small to see with our eyes.