252
IONISATION, DIFFUSION, ROTATION
This is an example of conditions giving a rather clean ionisation since
the ionisations in progress are mostly confined to a narrow range of energy
A = 1-2 to 1*9 A. The removal of electrons from deeper energy levels has
scarcely begun and removal from higher levels is nearly complete. Only
those electrons, if any, at an energy level within these limits require
detailed consideration. How this affects the atoms of different elements
will be seen from Table 30. For titanium (Z = 22) the last K electron is
detached at A = T9, so that for titanium and lighter elements the final
ionisation is very far advanced and the ions are mostly bare nuclei. After
titanium there will be a short sequence of elements in critical condition
as regards K ionisation and retaining mostly 1 or 2 A electrons; the sequence
ends at zinc (Z = 30) for which the first K ionisation requires T3 A so that
x is not much more than fa. Then follows a much longer sequence
Z = 31-45 for which the range A = 1-2-1-9 falls in the gap between
the K and L ionisations; these will be practically all helium-like ions
retaining two K but no L electrons. For rhodium (Z = 45) the last L
ionisation is fa complete. Elements from 45 to 73 are in various stages of
L ionisation; for tantalum (Z = 73) the first L ionisation is only t l com
plete. Here we reach the gap between L and M ionisation and the ions
are neon-like retaining 10 electrons. The heaviest elements may retain
two or three M electrons*.
Table 30.
Energy Levels. Wave-lengths in Angstroms.
z
Elem.
K
K'
L'
M 1
M'
A T i
Z + l, 2,
3
13
A1
7-95
5-39
175
30
Si
P
S
17
Cl
4-38
3-15
62-0
16-2
—
—
—
A
K
Ca
21
Sc
2-75
2-07
30-4
10-1
—
—
—
Ti
V
Cr
25
Mn
1-89
1-46
19-05
6-89
—
—
—
Fe
Co
Ni
29
Cu
1-38
1-08
13-05
5-00
—
—
—
Zn
Ga
Ge
33
As
1-04
•84
—
3-79
—
—
—
Se
Br
Kr
37
Rb
•814
•666
—
2-97
—
—
—
Sr
Y
Zr
41
Nb
•650
•542
5-22
2-40
611
8-5
—
Mo
—
Ru
45
Rh
•533
•450
4-13
1-97
41-0
—
—
Pd
Ag
Cd
49
In
•443
—
3-30
1-65
—
—
—
Sn
Sb
Te
53
I
•373
—
2-71
1-40
21-5
4-44
—
X
Cs
Ba
57
La
•319
—
2-25
1-20
14-8
3-71
—
Ce
Pr
Nd
61
—
•274
—
1-91
1-04
11-9
3-15
—
Sm
Eu
Gd
65
Tb
•238
—
1-64
•92
9-96
2-71
—
Ds
Ho
Er
69
Tm
•208
—
1-43
—
8-40
2-35
—
Yb
Lu
Hf
73
Ta
•184
—
1-25
—
7-14
2-07
415
W
—
Os
77
Ir
•163
—
110
—
6-08
1-83
—
Pt
Au
Hg
81
T1
•143
—
•98
—
5-16
1-63
95
Pb
—
83
Bi
•136
—
•92
—
4-76
1-54
70-0
Po
—
Nt
92
U
•107
•107
•72
•45
3-49
1-22
330
—
—
—
* These conclusions being based on a first approximation are subject to revision.