Consider these 4 transitions for an electron in a hydrogen atom. I) n = 7 --> n = 1 II) n = 7 --> n = 5 III) n = 1 --> n = 7 IV) n = 7 --> n = 6. Of those that will emit of photon, which will emit a photon with the longest wavelength?

Respuesta :

Explanation:

Using Reydberg's equation, we will calculate the energy emitted by the photon for the given transitions.

The equation is as follows.

         [tex]\Delta E = -2.178 \times 10^{-18} J \times (Z)^{2}[\frac{1}{n^{2}_{2}} - \frac{1}{n^{2}_{1}}][/tex]

1).  For [tex]n_{1}[/tex] = 7,    [tex]n_{2}[/tex] = 1,         Z for H = 1                          [tex]\Delta E = -2.178 \times 10^{-18} J \times (Z)^{2}[\frac{1}{n^{2}_{2}} - \frac{1}{n^{2}_{1}}][/tex]

= [tex]-2.178 \times 10^{-18} J \times (1)^{2}[\frac{1}{(1)^{2}} - \frac{1}{(7)^{2}}][/tex]

                  = [tex]-2.178 \times 10^{-18} J \times (1 - 0.02)[/tex]

                  = [tex]-12.13 \times 10^{-18} J[/tex]  

As,     E = [tex]\frac{hc}{\lambda}[/tex]  

Putting the given values and calculate the wavelength as follows.

                E = [tex]\frac{hc}{\lambda}[/tex]  

[tex]12.13 \times 10^{-18} J[/tex] = [tex]\frac{6.626 \times 10^{-34}Js \times 3 \times 10^{8 m/s}}{\lambda}[/tex] 

        [tex]\lambda = 1.58 \times 10^{-8}[/tex] m

                      = [tex]15.8 \times 10^{-9}[/tex] m

                      = 15.8 nm       (as 1 m = [tex]10^{-9}[/tex] nm)

2).  For [tex]n_{1}[/tex] = 7,    [tex]n_{2}[/tex] = 5,         Z for H = 1                   [tex]\Delta E = -2.178 \times 10^{-18} J \times (Z)^{2}[\frac{1}{n^{2}_{2}} - \frac{1}{n^{2}_{1}}][/tex]

= [tex]-2.178 \times 10^{-18} J \times (1)^{2}[\frac{1}{(5)^{2}} - \frac{1}{(7)^{2}}][/tex]

                  = [tex]-2.178 \times 10^{-18} J \times (0.04 - 0.02)[/tex]

                  = [tex]-0.0435 \times 10^{-18} J[/tex]  

As,     E = [tex]\frac{hc}{\lambda}[/tex]  

Putting the given values and calculate the wavelength as follows.

                E = [tex]\frac{hc}{\lambda}[/tex]  

   [tex]0.0435 \times 10^{-18} J[/tex] = [tex]\frac{6.626 \times 10^{-34}Js \times 3 \times 10^{8 m/s}}{\lambda}[/tex]   

                [tex]\lambda = 456.9 \times 10^{-8}[/tex] m

                             = 45.6 nm

3).  For [tex]n_{1}[/tex] = 1,    [tex]n_{2}[/tex] = 7,         Z for H = 1                     [tex]\Delta E = -2.178 \times 10^{-18} J \times (Z)^{2}[\frac{1}{n^{2}_{2}} - \frac{1}{n^{2}_{1}}][/tex]

= [tex]-2.178 \times 10^{-18} J \times (1)^{2}[\frac{1}{(7)^{2}} - \frac{1}{(1)^{2}}][/tex]

                  = [tex]-2.178 \times 10^{-18} J \times (0.02 - 1)[/tex]

                  = [tex]2.13 \times 10^{-18} J[/tex]  

As,     E = [tex]\frac{hc}{\lambda}[/tex]  

Putting the given values and calculate the wavelength as follows.

                E = [tex]\frac{hc}{\lambda}[/tex]  

    [tex]2.13 \times 10^{-18} J[/tex] = [tex]\frac{6.626 \times 10^{-34}Js \times 3 \times 10^{8 m/s}}{\lambda}[/tex]     

                [tex]\lambda = 9.33 \times 10^{-8}[/tex] m

                             = 93.3 nm

4).  For [tex]n_{1}[/tex] = 7,  [tex]n_{2}[/tex] = 6,         Z for H = 1                [tex]\Delta E = -2.178 \times 10^{-18} J \times (Z)^{2}[\frac{1}{n^{2}_{2}} - \frac{1}{n^{2}_{1}}][/tex]

= [tex]-2.178 \times 10^{-18} J \times (1)^{2}[\frac{1}{(6)^{2}} - \frac{1}{(7)^{2}}][/tex]

                  = [tex]-2.178 \times 10^{-18} J \times (0.03 - 0.02)[/tex]

                  = [tex]-0.0217 \times 10^{-18} J[/tex]  

As,     E = [tex]\frac{hc}{\lambda}[/tex]  

Putting the given values and calculate the wavelength as follows.

                E = [tex]\frac{hc}{\lambda}[/tex]  

   [tex]0.0217 \times 10^{-18}J[/tex] = [tex]\frac{6.626 \times 10^{-34}Js \times 3 \times 10^{8 m/s}}{\lambda}[/tex]    

                [tex]\lambda = 916.03 \times 10^{-8}[/tex] m

                             = 9160.3 nm

Thus, we can conclude that transition from n = 7 to n = 6 will emit a photon with the longest wavelength.