A sample of nitrogen gas occupies a volume of 2.00 L at 756 mm Hg and 0.00°C. The volume increases by 2.00 L and the
temperature decreases to 137 K What is the final pressure
exerted on the gas?

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