Which of the following is characteristic of all reversible systems at equilibrium?
activation energy is not required.
changes do not occur at the microscopic level.
two opposing reactions occur at the same rate.
they occur in open systems.
a catalyst affects the forward reaction.

Two opposing reactions occur at the same rate

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There is one s orbital, and there are three p orbitals, five d orbitals, and seven f orbitals. thus, the answer is b. do not confuse the number of orbitals in a subshell with the number of electrons the subshell can hold. each orbital can hold two electrons, so the capacity of an nf subshell is 14 electrons.