what are the
characteristics
of an atom?

The characteristics are as follows:

-It is microscopic.

-It contains three sub atomic particles namely: electrons, protons and neutrons.

-It is the smallest unit of any substance (except for living bodies since smallest unit of them is cell).

-When seen from microscope atoms appear to be blur, spheres.

-They form ions(by losing or gaining electrons) and molecules(by combining with itself or other atoms).

Hope this helps :)

its weight is greatest on earth

the answer would be c