The periodic table displays a. only the important compounds that exist in the world. b. only the important elements that exist in the world. c. all of the known elements that exist in the world today. d. all of the known compounds that exist in the world today.

all of the known elements that exist in the world today.

Explanation:

The periodic table is arrangement of elements based on the atomic number of elements. It is a periodic arrangement of physical and chemical properties of elements. So far we have 118 elements in the modern periodic table.

The compounds are formed from these elements arranged in periodic table. Thus we can say that it displays all of the known elements that exist in the world today.

yes it is balanced

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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