The energy levels of the dication of lithium (Li 2+ ) aredescribed by slight mod

Question

The energy levels of the dication of lithium (Li2+) aredescribed by slight modification of those for H-atom: All theenergy levels are nine times those of the H atom. What is thewavelength (in nm) emitted by Li2+ in going from n=5 ton=4?

a) 225 nm
b) 450 nm
c) 520 nm
d) 810 nm
e) 900 nm

Is the Balmer-Rydberg equation suitable only for H atoms? I THINKit's answer 450...I used it for the above conditions, and dividedby 9 to get the answer. But I don't understand why and if it'scorrect...please reply & explain! Thanks.

Explanation / Answer

We know that ,   1 / = R [ ( 1/n2 ) - ( 1/ n' 2 ) ] Where R = Rydburg's constant = 10.9678 * 10^6 m^-1            = wave length = ?           n =4           n' =5 Plug the values we get     1 / = 10.9678 * 10^6 * [ ( 1/42 ) - ( 1/ 5 2 ) ]                                               = 0.2467755 *10^6                                             = 4.052 * 10^-6 m                                               = 4.052 * 10^-6 * 10^-3 * 10^3 m                                               = 4052 * 10^-9 m                                               = 4052 nm So the required wavelength , ' = 4052 / 9 = 450nm

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---