AP Biology homework helppp!?

Hey, I need help with my AP bio homework. I'm not sure how to answer these questions. Thank you in advance. Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is: A an electron may move to an electron shell farther out from the... show more Hey, I need help with my AP bio homework. I'm not sure how to answer these questions. Thank you in advance.

Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is:
A an electron may move to an electron shell farther out from the nucleus
B an electron may move to an electron shell closer to the nucleus.
C the atom may become a radioactive isotope.
D the atom would become a positively charged ion, or cation.
E the atom would become a negatively charged ion, or anion.


What do the four most abundant elements in life-carbon, oxygen, hydrogen, and nitrogen- have in common?
A They're elements only produced by living cells.
B Each element exists only in one isotopic form
C They all have unpaired electrons in their valence shells
D They are equal in electronegativity

Which atom is the cation in in ammonium chloride salt?
A CL
B N
C H
D NH4
E NH4CL

Each element in unique and different from other elements because of its
A atomic weight
B atomic number
C mass number
D only A and B are correct
E A, B, C are correct


Thanks...
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