Download E = 3.026 x 10 J - since the electron goes from a lower n to a higher

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Homework 5
1.) A Hydrogen electron makes a transition from n=2 to n=3. Calculate the energy, frequency, and
wavelength of the photon. In what region of the spectrum is this photon?
 1
1 
E = -2.179 x 10-18 J  2 − 2 
 nH nL 
 1
1 
E = -2.179 x 10-18 J  2 − 2  = -2.179 x 10-18 J (-0.1388888)
3
2 

E = 3.026 x 10-19 J - since the electron goes from a lower n to a higher n, E
will be positive
 1
1
1 
= 1.0968 x 10 7 m - 1  2 − 2 
λ
 n1 n2 
 1
1
1 
= 1.0968 x 10 7 m - 1  2 − 2  = 1.0968 x 107m-1 (0.138888888)
3
2 
λ

1
= 1.5233 x 106 m-1
λ
λ=
1
=
1.5233 x 10 6 m −1
6.5645 x 10-7 m - this is in the visible region (656.45 nm)
c = λυ
υ = c/λ = 2.9979 x 108m/s / 6.5645 x 10-7 m = 4.5668
x 1014 sec-1
Or
E = hυ
υ = E/h = 3.026 x 10-19 J/6.626 x 10-34 Jsec = 4.567
x 1014 sec-1
2.) Which of the following quantum number sets are allowed? If there is an error identify AND
correct it with a valid quantum number – each incorrect set, only contains ONE error, therefore
only change ONE of the quantum numbers to make the set valid. If the set is valid, write the word
valid or ok after it!
a. n= 2, l= 1, ml= 0: valid
b. n= 2, l= 2, ml = 2: not valid – l and n cannot be the same number n = 3 (or greater)
c. n= 6, l= 4, ml= -5: not valid, ml cannot be outside –l . . .+ l therefore l = 5 ok or ml
betweent -4 . . . +4
d. n=6,
l=5, ml = -4: valid
3.) Write the electron configurations for
2
2
6
2
6
2
10
2
2
6
2
6
2
9
2
2
6
2
6
2
4
2
2
6
1
a. Zn: 1s 2s 2p 3s 3p 4s 3d
b. Cu: 1s 2s 2p 3s 3p 4s 3d
BUT!! Becomes 4s13d10
1
5
c. Cr: 1s 2s 2p 3s 3p 4s 3d BUT!! Becomes 4s 3d
d. Na: 1s 2s 2p 3s
4.) Using the electron configuration for Zn, draw all the orbital box diagrams. Write the complete set
of quantum numbers for electrons 1, 5, 9, 21, and 26
1
5
1s
9
2s
2p
3s
21
3p
4s
26
3d
n, l, ml, ms
1st: 1, 0, 0, + ½
5th: 2, 1, -1, + ½
9th: 2, 1, 0, - ½
21st: 3, 2, -2, + ½
26th: 3, 2, -2, - ½