A covenant bond is formed when electrons move from one element to another.
<span> Advantage: CO2 isn't as toxic as CO. Disadvantages: Can get a mixture of oxygen isotopes in CO2, so some species would effuse at about the same rate." But I'm jumping into AP Chem with no prior knowledge so I don't understand anything.</span>
Answer: compound
Explanation: because the hydrogen molecules and the oxygen molecules are chemically bonded together unlike in a mixture
The answer to your question is dependent variable.
The atmosphere is considered homogeneous. It isn’t exactly on the smallest scales but that doesn’t matter. Homogenous means the composition will be the same in any sample taken from the substance. And clearly, the atmosphere is mostly gas. So the last answer is right