Chemistry Reference
In-Depth Information
1
2
H
He
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
11
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
87
88
89
Fr
Ra
Ac
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Tb
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Dy
Ho
Er
Tm
Yb
Lu
90
91
92
93
94
95
96
97
98
99
100
101
102
103
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Figure B.1
Periodic Table of the elements. The atomic number of each element is given in
the top left hand corner of its box, with the chemical symbol in the box centre.
The elements are arranged in columns predominantly reflecting the order in
which electronic subshells are filled: s states (
l
0) filling in the first two
=
columns; p-states (
l
1) in the six right-hand columns, with d-state (
l
2)
=
=
filling in columns 3-12, and f-state filling (
l
=
3) indicated in the 'footnote' to
the Table.
Figure B.1 presents the Periodic Table of the elements. The analysis
we have presented here accounts for most of the trends observed in the
Periodic Table, which we assume and use throughout this topic:
1
In a many-electron atom, the lowest energy states typically experience
a very strong attractive potential due to the positively charged nucleus.
These states therefore have a much larger binding energy than the
highest filled levels. They are referred to as
core
states. They are highly
localised and make no direct contribution to bonding in a solid.
2
The core electrons screen the attractive potential seen by the higher
filled states. We can compare, for example, carbon
(
C,
Z
=
6
)
with
silicon
. For C, the two filled
1s states at least partly cancel the attraction due to two of the six nuclear
protons, so that the 2s and 2p states experience an average attractive
potential equivalent to of order four protons. In Si, the filled 2s and
2p states also contribute to the screening, so that the 3s and 3p states
again experience an average attractive potential equivalent to of order
four protons. Likewise in Ge, the filled
n
(
Si,
Z
=
14
)
and germanium
(
Ge,
Z
=
32
)
3 shell (3s, 3p, 3d states)
contributes to screening, leaving a similar net attractive potential to
=
