atomic structure

Li+2 ion is hydrogenic and has a Lyman seriies at 740747cm-1,877924cm-1,925933cm-1 and beyond.Show tht the energy levels are of the form -R/n2 and find the value of R for this ion. Predict the wave no's of the two longest wavelength transition of the Balmer series of the ion and find the ionisation energy of the ion?

2 Answers

62
Lokesh Verma ·

1/λ1=R(1/1-1/22)
1/λ1=.75R
1/λ2=R(1/1-1/32)
1/λ2=8/9R
1/λ3=R(1/1-1/42)
1/λ1=15/16R

Now take the ratios

1/λ1:1/λ2:1/λ3 = 4/3:9/8:16/15

we compare the lamda's above.. the ratio is the same..

so we have shown that the energy levels are as needed!

62
Lokesh Verma ·

1/λ1=R(1/1-1/22) = 4/3R

We know λ1

so we know R

last part follows simply by taking appropirate n1 and n2

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