Before free oxygen gas became abundant in the oceans and atmosphere, it reacted with a metal and produced what type of formations?
a. the ionosphere
b. the ozone layer
c. banded iron formations
d. stromatolites

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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.