CHEM 1411
practice problem of chap7
1. *What is the frequency of 500nm?(the speed of light is 3.00 x 10 8m/s)
(a) 6.00 x 10 18
(b) 12.00 x 10 14
(c) 6.00 x 10 14
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(d) 8.00 x 10
(e) 6.00 x 10
Hint: ν=c / λ=(3.00 x 10 8m/s)/ 500 x 10 -9m=6.00 x 10 14
2. *Calculate the energy (in joules) associated with the photons if the wavelength of the X
rays is 0.154 nm.
(a) 1.29 x 10 -15 (b) 8.70 x 10 -15 (c)1.29 x 10 -18 (d)4.35 x 10 -25 (e)2.79 x 10 -30
Hint: E = h x c / λ,
E = 6.63 x 10-34 (J•s) x 3.00 x 10 8 (m/s) / 0.154 x 10-9 (m)= 1.29 x 10 -15 J
3. Which of the following statements concerning four quantum numbers is correct?
(a) The angular (i.e. azimuthal) quantum number, l, determines the energy of an electron in a
hydrogen atom and in a many-electron atom.
(b) The principle quantum number, n, determines the shape of an orbital.
(c) The electron spin quantum number, ms, determines the orientation of an orbital in space.
(d) The magnetic quantum number, ml, determines the size of an orbital.
(e) The principle quantum number, n, determines the size of an atom.
Hint: p.p. 286-288: Definitions.
4. What values of the angular momentum (l) quantum numbers are allowed for n=4?
(a) -4,-3,-2,-1 (b) 0.1,2,3,4 (c)0,1,2,3
(d) -3,-2,-1,0,1,2,3
Hint: Allowed values:
• n = 1,2,3 …,n; l = 0,1,2,…,(n-1); ml = (-l, …, 0. …+l); ms = +1/2, -1/2
5. Which of the following four quantum numbers (n, l, ml, ms) does not represent an
electron in a 3d orbital?
(a) (3, 2, -1, +½)
(b) (3, 2, -2, -½)
(c) (3, 2, 0, -½)
(d) (3, 2, +1, +½)
(e) (3, 1, +1, +½)
Hint: p.p. 286-288, p. 292: Definitions and examples 7.6 & 7.8. For d orbital, l=2
6. *Which of the following sets of quantum numbers in an atom is acceptable?
(a) (1, 0, +½, +½)
(b) (3, 2, -2, -½)
(c) (3, 3, 0, -½).
(d) (4, 2, +3, +½)
(e) (3, 0, +1, +½)
p.p. 286-288: Definitions and example 7.6 and p. 292. See allowed values for quantum
numbers
7. Which of the following is a correct ground-state electron configuration?
(a) Al: 1s22s22p43s23p3
(b) B: 1s22s22p5
(c) F: 1s22s22p6
2 2
6 1
1
2 2
6 2
5
(d) Mg: 1s 2s 2p 3s 3p
(e) Cl: 1s 2s 2p 3s 3p
Hint: p.p. 292-294.
8. *How many unpaired electrons are present in Al?
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5
2 2
6 2
Hint: p.p. 295-298. Electron configuration or p. 300. Al: 1s 2s 2p 3s 3p1
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9. Which family of elements is characterized by having an ns2np1outer-electron
configuration?
a) Group IA
b) Group IIA c) Group IIIA
d) Group II B
10. What is the maximum number of electrons in an atom that has the quantum numbers as
n=2, l=0, ms= +½?
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5
Hint: Practice problem of chap7 Q2; Due to the limit of ms. Compare with Example 7. 10
and p. 306: 7.96.
11. *Which of the following violates the Pauli Exclusion Principle?
(a) ↑ ↑__ ↑↑
(b) ↑ ↑↓ ↑_
(c) ↑ ↑↓ ↓_
(d) ↑↓_ __ ↑ _ ↑_ ↑_
(e) ↑_ ↑__ ↑ _ ↓_ ↑↓_
Hint: Check the orbital that has two electrons in it. Pauli Exclusion Principle : no two
electrons in an atom can have the same four quantum numbers. The electrons must be spinpaired (i.e. opposite directions), p. 293 and p. 308: 7.124.
12. *Which of the following violates the Hund’s rule?
(a) ↑ ↑__ ↑↑
(b) ↑ ↑↓ ↑_
(c) ↑ ↑↓ ↓_
(d) ↑↓_ __ ↑ _ ↑_ ↑_
(e) ↑_ ↑__ ↑ _ ↓_ ↑↓_
Hint: p. 308: 7.124. Check the degenerate orbitals like p, d, and f. Each of the orbitals must
have one electron in it before putting the second electron in it. It does not matter whether the
two electrons are in opposite directions or not.
13. What is the maximum number of electrons in an atom that has the quantum numbers as
n=4, ml= +1?
(a) 2
(b) 4
(c) 6
(d) 8
(e) 10
Hint: Identify total orbitals in there according to l. Since here specify that the ml= +1, which
indicates that the l = 1 and thus there are total three ml values, that is, -1, 0 and +1. Thus,
maximum six electrons. Compare with Examples 7.6, 7.7, 7.8, 7.9 and 7.10, and p. 306: 7.96.
14. Which of the following is paramagnetic?
(a)He (b)Be (c)B (d)Ne (e)Mg
Hint: paramagnetic substance should have unpaired electrons. He 1s2 ; Be 1s22s2 ; B
1s22s22p1 ; Ne 1s22s22p6 ;Mg: 1s22s22p63s2
15. *Calculate the wavelength (in nm) of a photon emitted by a hydrogen atom when its
electron drops from the n = 5 state to the n = 3 state.
(a) 264
(b)1280
(c)4598
(d) 6789
(e)9056
Hint: p.p.277. Example7.4
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