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The ionization potential of hydrogenic ions P and Q are V_P and V_Q respectively. If V_Q<V_P then radii

Asked in GUJCET 2017 · Energy levels and ionisation

Answer: (2) r_P<r_Q

Step-by-step solution

Given: two hydrogen-like ions with V_Q<V_P. Ionisation is from the ground state, so the radii are ground-state radii.

Idea: for a one-electron ion, Bohr's model gives V=13.6 Z² V and r=(a₀)/Z in the ground state.

V_Q<V_P means Z_Q<Z_P.

A smaller Z gives a larger orbit, so r_Q>r_P.

Therefore r_P<r_Q: the ion with the higher ionisation potential has the smaller radius, since V∝1/(r²).

Why the other options are wrong

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