If two atoms have the same atomic numbers but different mass numbers, then they can be considered atoms of the same element. true or false

True.

Explanation:

If two atoms have the same atomic number, they have the same number of protons in the nucleus.

The number of protons derermines the identity of an atom.

So, two atoms with the same atomic number are the same element.

  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-