Structure of Atom - Result Question 20

####20. If ionization potential for hydrogen atom is 13.6eV, then ionization potential for He+will be

(a) 54.4eV

(b) 6.8eV

(c) 13.6eV

(d) 24.5eV

[1993]

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Solution:

  1. (a) The ionization energy of any hydrogen like species (having one electron only) is given by the equation

I.E =2π2Z2me4h2 or I.E Z2

Since the atomic number of H is 1 and that of He is 2 , therefore, the I.E. of He+is four times (22) the I.E. of Hi.e., 13.6×4=54.4eV

For H-like particles,

En=21.8×1019h2Z2J/ atom

=1312n2Z2kJ/mol

I.E=EaoE1=0(IEHZ2)

=Z2×IEH

Now for He+,Z=2I.E=4×IH

 for Li2+,Z=3I.E=9×IH



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