In the atmosphere, it is more common to find two oxygen molecules joined together than to find a single atom of oxygen. Why? What would that molecule look like? What would this molecule be called?

See explanation

Explanation:

Oxygen has six electrons in its outermost shell. This means that its octet can be completed when it shares two electrons with another oxygen atom.

In a covalent bond, each bonding atom contributes one electron to the bond. This means that four electrons are shared between two oxygen atoms. Each atom contributes a total of two electrons which are shared. This molecule of oxygen satisfies the octet rule rather than a single atom of oxygen.

An image of the oxygen molecule is attached to this answer.

This system of two oxygen atoms joined together in a covalent bond is called an oxygen molecule(O2).

  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-

since electrons are negative the answer is neagtaive