The equation for the chemical reaction shown below is not balanced. what number should replace the question mark to balance this equation? 2al + ? cl2 → 2alcl3 a. the number 2 b. the number 3 c. the number 4 d. the number 5

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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