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 :)

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of c is as shown here in the image.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-