A sample of Ac-255 originally contained 8.0g. After 720 hours, how much of the original Ac-255 remains? The half-life of the isotope is 10 days.

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.

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