The mass numbers for two isotopes are unequal because they have different numbers of NEUTRONS.
C. atoms of reactants rearrange to form new substances
Answer:
key concepts and summary. When electrons move from a higher energy level to a lower one, photons are emitted, and an emission line can be seen in the spectrum. Absorption lines are seen when electrons absorb photons and move to higher energy levels
Explanation:
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<h2>Answer : Option B) Ozone</h2><h3>Explanation :</h3>
The layer of atmosphere which contains a substance(Ozone) that was created from a product of living thins (oxygen) and protects living things (from harmful UV rays).
Oxygen in the atmosphere reacts in presence of UV rays and forms Ozone.
This ozone forms a protective layer around the earth and protects it from harmful UV rays.