Is this reaction oxidation or reduction
CH2=CH2 + OsO4 yields to HOCH2CH2OH

it's definitely a oxidation reaction because here the oxygen contained OH group present in yeild

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.