Answer:
n=3
Explanation:
The expression for the energy of an electron for the hydrogen atom in the nth orbit is:-
Given that:-
Applying in the equation to find the value of n as:-


I think it could be letter B
B. A current in charges change direction
Explanation: an electric current that reverses its direction many times a second at regular intervals, typically used in power supplies.
The elements that form anions will have the electronic configuration similar to the noble gas that is in their period and those that form cations will have a configuration similar to that of the noble gas in the previous period.
He: Be
Ne: F, Al
Ar: Ca, P
Kr: Rb, Se
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