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.

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.