An element is BEST described as a substance that: is made of atoms
Cannot be broken down into other substances
Contains water
Is a metal used in kettles​

Cannot be broken down into other substances

Explanation:

there is none because earth is stationary and flat.

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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~ trueboss72