Oxygen gas was most likely absent from Earth's primitive atmosphere. The current theory is that the Earth's early atmosphere was composed of mainly carbon dioxide and methane due to the high volcanic activity. Cyanobacteria and their use of photosynthesis was what caused earth's atmosphere to become oxygen enriched.
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Answer:
Carbon and Oxygen, Argon and Helium.
Explanation:
noble gases have full outer shells of electrons, and so cannot share other atoms' electrons to form bonds. sodium and chlorine form an ionic bond.
CaCl2 is a good conductor of electricity when dissolved in water.
Answer:
Law
Explanation:
A law is a summary of observed (measurable) behavior, whereas a theory is an explanation of behavior. A law tells what happens; a theory (model) is our attempt to explain why it happens.
