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.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

can you attach the