# How much energy is required to ionise an H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom. - Chemistry

Numerical

How much energy is required to ionise an H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n =1 orbit).

#### Solution

The expression of energy is given by,

"E"_"n" = (-(2.18xx10^(-18))"Z"^2)/"n"^2

Where,

Z = atomic number of the atom

n = principal quantum number

For ionization from n1 = 5 to "n"_2 = ∞

triangle "E" = "E"_(∞) -  "E"_5

=[{{-(2.18xx10^(-18)J)(1)^2)/(∞)^2}-{(-(2.18xx10^(-18)J(1)^2))/(5)^2}]

= (2.18xx10^(-18)"J")(1/((5)^2))      ("Since" 1/∞ = 0)

= 0.0872 xx 10^(-18) "J"

triangle "E" = 8.72 xx 10^(-20) "J"

Hence, the energy required for ionization from n = 5 to n = ∞ is 8.72 × 10–20 J.

Energy required for n1 = 1 to n = ∞

triangle "E'" = "E"_(∞) - "E"_1

= [{(-(2.18xx10^(-18))(1)^2)/(∞)^2}-{(-(2.18xx10^(-18))(1)^2)/(1)^2}]

= (2.18 xx 10^(-18)) [1 - 0]

= 2.18 xx 10^(-18) "J"

Hence, less energy is required to ionize an electron in the 5th orbital of hydrogen atom as compared to that in the ground state.

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Chapter 2: Structure of Atom - EXERCISES [Page 70]

#### APPEARS IN

NCERT Chemistry Part 1 and 2 Class 11
Chapter 2 Structure of Atom
EXERCISES | Q 2.14 | Page 70

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