Chem 161-2007 Quiz 3
Version A1
1.
Give the noble gas ground state electronic configuration of the following atoms/ions using the
spdf
and
orbital diagram
notation.
spdf
notation
orbital diagram
Br
35
Br
[Ar]4s
2
3d
10
4p
5
[Ar]
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
↑↓
↑
O
2-
8
O
2-
[He]2s
2
2p
4
→ [He]2s
2
2p
6
≡ [Ne]
[He]
↑↓
↑↓
↑↓
↑↓
Cr
24
Cr
[Ar]4s
2
3d
4
→ [Ar]4s
1
3d
5
[Ar]
↑
↑
↑
↑
↑
↑
Fe
2+
26
Fe
[Ar]4s
2
3d
6
→ [Ar]4s
0
3d
6
≡ [Ar]3d
6
[Ar]
↑↓
↑
↑
↑
↑
2.
What is the maximum number of electrons in an atom that can have the following quantum numbers?
The question would have been better stated as, “What is the maximum number of electrons in an atom in
which the electrons have the following quantum numbers?”
a)
n
= 4 : This is the 4
th
principal shell.
The fourth principal shell has 1 s orbital, 3 p orbitals, 5 d orbitals
and 7 f orbitals, i.e., 16 orbitals.
Each orbital has 2 electrons.
Therefore, there are 32 4n electrons.
Using quantum mechanical formulas: If
n
= 4, then
l
= 0 to 3, or 0, 1, 2 and 3.
When
l
= 0, then
m
l
= -0 to
+0, = 1 orbital.
When
l
= 1, then
m
l
= -1 to +1, = -1, 0, +1, = 3 orbitals.
When
l
= 2, then
m
l
= -2, -1, 0,
+1, +2 = 5 orbitals.
When
l
= 3, then
m
l
= -3, -2, -1, 0, +1, +2, +3 = 7 orbitals.
Altogether there are 16
orbitals.
Since each orbital contains electrons of spin +1/2 and -1/2, then there are 32 4n electrons.
If this problem were interpreted to mean how many electrons are in the entire atom, i.e., in principal shells
1, 2, 3 and 4, then there are correspondingly 2, 8, 18 and 32 = 60 electrons.
b)
n
= 3,
l
= 2
Regardless of the number of the principal shell, l = 2 means d orbitals.
There are five d orbitals (-2, -1, 0,
+1, +2).
Each d orbital contains 2 electrons.
Therefore there are 10 electrons in
l
= 2.
c)
n
= 4,
l
= 2,
m
l
= 2,
m
s
= ½
When
l
= 2,
m
l
= -2, -1, 0, +1, +2.
When we define
m
l
as being 2, it just identifies one of the five d
orbitals.
Since we have identified the spin as being +1/2 in that single d orbital, then we have identified
the home of a single electron,
3.
In 10 words or less define the following:
a) Wave-particle duality: A light wave can behave as a particle, as demonstrated by a “packet of energy”
exciting an electron.
A particle (matter) can behave as a light wave, for example, when an electron
undergoes diffraction, with a demonstrable wavelength.
DeBroglie developed a formula showing the
convertibility of light and matter (or correspondingly, waves and particles): λ=h/mv.
b) Valence electron: the electrons in the highest principal quantum number, n, that is, the ones in the
outermost occupied principal shell of an atom.
c) Paramagnetic: the attraction into an external magnetic field of substances that have unpaired electrons.
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