The electron, its isolation and measurement and the determination of some of its properties
John Stuart Mill · en
The principle of the conservation of momentum accordingly demands
that the momentum of recoil of the scattering electron shall equal
the vector difference between the momenta of these two rays, as in
[Pg 285]
Fig. 42B. The momentum of the electron,
,
is thus given by the relation
where is the ratio of the velocity of recoil of the electron
to the velocity of light. But the energy in the scattered
quantum is equal to that of the incident quantum less the
kinetic energy of recoil of the scattering electron, i.e.,
We thus have two independent equations containing the two unknown
quantities and . On solving the equations we find
where
or, in terms of wave-length instead of frequency,
Substituting the accepted values of , , and ,
[Pg 286]
APPENDIX I
THE ELEMENTS, THEIR ATOMIC NUMBERS, ATOMIC WEIGHTS, AND CHEMICAL
POSITIONS
1 H
1.008
0
I
II
III
IV
V
VI
VII
VIII
2 He
3.99
3 Li
6.94
4 Be
9.1
5 B
11.0
6 C
12.00
7 N
14.01
8 O
16.00
9 F
19.0
10 Ne
20.2
11 Na
23.00
12 Mg
24.32
13 Al
27.1
14 Si
28.3
5 P
31.04
16 S
32.06
17 Cl
35.46
18 A
39.88
19 K
39.10
20 Ca
40.07
21 Sc
44.1
22 Ti
48.1
23 V
51.0
24 Cr
52.0
25 Mn
54.93
26 Fe 27 Co 28 Ni
55.84 58.97 58.68
29 Cu
63.57
30 Zn
65.37
31 Ga
69.9
32 Ge
72.5
33 As
74.96
34 Se
79.2
35 Br
79.92
36 Kr
82.92
37 Rb
85.45
38 Sr
87.63
39 Y
88.7
40 Zr
90.6
41 Nb
93.5
42 Mo
96.0
43—
44 Ru 45 Rh 46 Pd
101.7 102.9 106.7
47 Ag
107.88
48 Cd
112.40
49 In
114.8
50 Sn
118.7
51 Sb
120.2
52 Te
127.5
53 J
126.92
54 X
130.2
55 Cs
132.81
56 Ba
137.37
57 La 58 Ce 59 Pr 60 Nd 61—62 Sm 63 Eu 64 Gd 65 Tb 66 Ds
139.0 140.25 140.6 144.3 150.4 152 157.0 159.2 162.5
67 Ho 68 Ev 69 Tu 70 Yb 71 Lu 72Hf
163.5 167.7 168.5 173.5 175.0
73 Ta
181.5
74 W
184.0
75—
76 Os 77 Ir 78 Pt
190.9 193.1 195.2
79 Au
197.2
80 Hg
200.6
81 Tl
204.0
82 Pb
207.20
83 Bi
208.0
84 Po
(210.0)
85—
86 Ni
(222.0)
87—
88 Ra
226.0
89 Ac
(227)
90 Th
232.15
91 Pa
(234)
92 U
238.2
Elements, the atomic numbers of which are not in the order of atomic
weights, are in italics. The numbers corresponding to missing elements
are in bold-faced type.
1 Hydrogen
24 Chromium
47 Silver
70 Ytterbium
2 Helium
25 Manganese
48 Cadmium
71 Lutecium
3 Lithium
26 Iron
49 Indium
72 Hafnium
4 Beryllium
27 Cobalt
50 Tin
73 Tantalum
5 Boron
28 Nickel
51 Antimony
74 Tungsten
6 Carbon
29 Copper
52 Tellurium
75 ——
7 Nitrogen
30 Zinc
53 Iodine
76 Osmium
8 Oxygen
31 Gallium
54 Xenon
77 Iridium
9 Fluorine
32 Germanium
55 Caesium
78 Platinum
10 Neon
33 Arsenic
56 Barium
79 Gold