How do you calculate the ionization energy of an element?

1 Answer
Doc048 · Michael
Dec 19, 2017

Use the Rydberg Equation #DeltaE_i# = #A(1/n_f^2 - 1/n_i^2)# where #A = 2.18xx10^-18"Joules"#; #n_f = oo#; #n_i = "starting energy level". #

Explanation:

For the Hydrogen Atom, ionization from the ground state where #n_i = 1# => #DeltaE_(izn)=2.18xx10^-18J(1/(oo)^2 - 1/(1)^2)# = #-2.18xx10^-18"Joules"# to remove the electron from n = 1 energy level to #n=oo#. The negative indicates that on 'gain' of electron, #2.18xx10^-18#Joules energy is released, but on removal, #DeltaE# should be greater than zero indicating the gain of energy to remove the electron. #Delta E_(removal)#=#DeltaE_("gained")#.

The #2.18xx10^-18# Joules is per atom#

=> #"Joules"/"mole"# = #(2.18xx10^-18 j/"atom")##(6.02xx10^23"atoms"/"mole")# = #1,351,600 "joules"/"mole" = #1352#"Kj"/"mole"#. This corresponds favorably with the published 1st ionization energy of the Hydrogen atom.

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