How many moles of electrons are required to reduce one mole of oxygen gas (o2) to two moles of oxygen ions (
2 e-
4 e-
6 e-
8 e-

The correct answer is 4 electrons.

Explanation:

Reduction reaction is defined as chemical reaction in which element gains electrons and it get reduced. Also oxidation state of that element also deceases.

Charge on both sides should be balanced so for that write 4 as a coefficient of en electron in an above reaction.By this the charge on booth sides becomes (4-).

1 mole of oxygen gas gets reduced by 4 electrons into 2 moles of oxygen  ions.

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.