The Current Oxygen Level in the Earth's Atmosphere Was Reached

question 8

Multiple Choice

The current oxygen level in the Earth's atmosphere was reached about

• A) 4.6 billion years ago.
• B) 2 billion years ago.
• C) 20 million years ago.
• D) 250 million years ago.
• E) 540 million years ago.

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Definitions:

Transition State

A high-energy state during a chemical reaction that represents the point of highest energy through which reactants must pass before forming products.

Resonance Stabilized Radical

A radical species whose stability is enhanced by the distribution of its unpaired electron over multiple atoms via resonance.

1-Butene

A simple aliphatic hydrocarbon with the formula C4H8, classified as an alkene due to the presence of a double bond between carbon atoms.

Br Radical

Bromine radical, a highly reactive species with an unpaired electron, resulting from the homolytic cleavage of bromine.