It is possible to determine the ionization energy for hydrogen using the Bohr equation. Calculate the ionization energy for an atom of hydrogen, making the assumption that ionization is the transition from n=1 to n=infinity.

A. -2.18 x 10-18 J
B. +2 .18 x 10-18 J
C. +4.59 x 10-18 J
D. -4.59 x 10-18 J
E. +4.36 x 10-18 J

Calculate the energy change associated with the transition from n=4 to n=1 in the hydrogen atom.

A. +4.89 x 10-18 J
B. +1.64 x 10-18 J
C. -6.12 x 10-18 J
D. +3.55 x 10-18 J
E. -2.04 x 10-18 J

Respuesta :

Answer:

B      E = 2.18 x 10⁻¹⁸ J

E      E = - 2.04 x 10⁻¹⁸ J

Explanation:

According to Bohr´s model ofthe atom the energy change  for  a given electronic transition between energy levels can be determined using the Rydberg´s equation . Therefore, the strategy here is to use Rydberg´s equation:

1/λ = Rh x ( 1/n₁² - 1/n₂² )

where Rh is Rydberg´s constant ( 1.097 x 10⁷ / m ), n₁  and n₂ are the energy levels in the transition, and λ is the wavelegth of the transition.

Once 1/λ is determined, we can calculate the ionization energy  using the  relation: E = h c/λ = E hc (1/λ ) , where h is Planck´s constant, and c is the speed of light.

1/λ = Rh x ( 1/n₁² - 1/n₂² ) = 1.097 x 10⁷ / m x ( 1/1² )      

The term 1/n₂² goes to zero as n₂ tends to infinity.

E = 6.626 x 10⁻³⁴ J·s x 3 x 10⁸ m/s x  1.097 x 10⁷ /m

E = 2.18 x 10⁻¹⁸ J

For the second part we use the same equation but with n₁ = 1 and n₂ = 4

1/λ = Rh x ( 1/n₁² - 1/n₂² )  =  1.097 x 10⁷ /m  x ( 1/1² -1/4² )

1/λ = 1.03 x 10⁷/m

E =  -6.626 x 10⁻³⁴ J·s x  3 x 10⁸ m/s x 1.03 x 10⁷ /m

E = - 2.04 x 10⁻¹⁸ J

(  When using Rydbergs equation by convention n₁ is the lowest energy level and the sign will always will come positive, but since here we are talking in going from  level 4 to level 1, energy will be released hence the negative sign )

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