How were you able to identify the periods?

This question is incomplete

Explanation:

This question is incomplete. However, the period of the periodic table are the horizontal (left to right) rows in the periodic table. Elements in the same period have the same number of electron shells. There are seven periods in the periodic table.

The periodic table of elements is the table that contains all chemical elements arranged according to there atomic number. Atomic number is the number of protons present in the nucleus of an atom.

  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-