NOVA scienceNOW | Amazing Atoms | PBS

"Here is the latest, atomically correct, version of our old friend, the atom."

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NOVA scienceNOW Amazing Atoms PBS.mp4

 

 

 

 

Ex) How much energy is absorbed when an electron in hydrogen moves from the energy levels n = 2 to n = 5?

 

Subtract the absolute values to find the energy needed to be absorbed

 

 

 

Answer

 

3.4 eV - .54 eV =  2.86 eV

 

 

 

 

Ex) How much energy is needed for an electron in the n = 1 energy level to move to the n = 2 energy level?

 

n = 1      -13.6 eV
 n = 2       -3.40 eV

 

 

 

Throw out the
negative signs and subtract

 

 

= 13.6 eV - 3.4 eV

= 10.2 eV Absorbed

 

 

 

Frequency of photon absorbed

E = hf

 

h = 6.63 x 10-34 Js

 

E = 10.2 eV

 

 

 

 

 

Convert eV to Joules

page 1 Reference

 

 

1 eV = 1.6 x 10-19 J

 

 

 

E = 10.2 eV x 1.6 x 10-19 J

 

= 1.6 x 10-18 Joules

 

 

 

E = hf

 

 

 

1.6 x 10-18 Joules =
 
(6.63 x 10-34 Js) f

 

 

 

 

f = 2.4 x 1015 Hz

 

 

 

 

Ex) Which energy level transition in MERCURY will produce a photon emission of .22 ev?

 

 

 

 

c to b transition

 

(Difference in energy
between b and c is .22 eV)

 

 

 

 

5) Ionization Energy - minimum energy needed to remove an electron from an atom.

 

 

 

Ionization Energy - greater than or equal to energy at that level.

 

 

 

 

 

 

 

Ionization Energy of Hydrogen

 

n = 1

 

 

13.6 eV or greater

 

 

 

n = 2

 

 

 

3.4 eV or greater

 

 

 

n = 3

 

 

1.51 eV or greater

 

 

 

 

 

Ex) A photon having an energy of 15.5 electron volts is incident upon a hydrogen atom in the ground state.

The photon may be absorbed by the atom and

 

a) ionize the atom

 

b) excite the atom to n = 3

 

c) excite the atom to n = 2   

 

d) excite the atom to n = 4

 

 

 

 

 

 

a) ionize the atom

 

 

 

 

 


 

 

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