1.

A hydrogen atom and Li^(++) ion are both in the second excited state. If l_(H) and l_(Li) are the respective electronic moments, and En and EL their respective energies then

Answer»

`l_(H) gt l_(Li) and |E_(H)| gt |E_(L)|`
`l_(H) =l_(Li) and |E_(H)| lt |E_(Li)|`
`l_(H)=l_(Li) and |E_(H)| gt |E_(Li)|`
`l_(H) lt L_(Li) and |E_(H)| lt |E_(Li)|`

Solution :According to Bohr, the angular momentum of an electron of HYDROGEN atom and hydrogen like atom `Li^(++)`,
`l =n (h)/(2PI)`
For both, n=2, `therefore l_(H)=l_(Li)=2 XX (h)/(2pi)=(h)/(pi)`
Energy of electron in nth orbit of hydrogen atom.
`E_H=-(13.6)/(n^(2)) eV`
For n=2, we get `E_(H)=-(13.6)/(4)-3.4eV`
Energy of electron in nth orbit of hydrogen like atom `("say "Li^(++) ion). E_(Li)=-(Z^(2) xx 13.6)/(2)eV`
Here n=2 and for Li, Z=3 `therefore E_(Li)=-(9 xx 13.6)/(2) -30.6eV`
i..e `|E_(H)| lt |E_(Li)|`


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