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Question
(a) Find the first excitation potential of He+ ion. (b) Find the ionization potential of Li++ion.
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Solution
(a) PE of hydrogen like atom in the nth state, V = `(-13.6Z^2)/n^2 eV`
Here, Z is the atomic number of that atom.
For the first excitation, the atom has to be excited from n = 1 to n = 2 state.
So, its excitation potential will be equal to the difference in the potential of the atom in n = 1 and in n = 2 states.
First excitation potential of He+
`- 13.6Z^2 (1 - 1/2^2) eV`
= `- 10.2 Z^2 eV `
`rArr 10.2 xx Z^2 `
`= 10.2 xx 4`
= 40.8 (b) Ionization Potential Li++ = 13.6 V ×Z2
= 13.6 × 9
= 122.4 V
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