History of periodic table part 3 - copy

History of the
Periodic Table
of the Elements
(CHEM 1360)
Part 3

Lavoisier’s Elements
“Elements in the body”
“Earths”
“Nonmetallic elements”
“Metallic elements”

John Dalton
Manchester, England
1810
“Atoms are featureless
spheres. The only
difference between
different elements
is their weight.
For example:
Hydrogen 1
Carbon 5
Oxygen 7
Phosphorus 9
Sulphur 13
Magnesia 20
Lime 24
Potash 42
Iron 50
Lead 90
Mercury 167
Gold 190”

These are models of atoms constructed by Dalton,
now on display in a Manchester museum.

Jöns Jacob Berzelius
Stockholm, Sweden
1826
Determined
Atomic
Weights Accurately

H 1 Li 7 Be 9.4 B 11 C 12
N 14 O 16 F 19 Na 23 Mg
24 Al 27.3 Si 28 P 31 S 32
Cl 35.5 K 39 Ca 40 Ti 48 V 51
Cr 52 Mn 55 Fe 56 Co 59
Ni 59 Cu 63 Zn 65 As 75 Se 78
Br 80 Rb 85 Sr 87 Y 88
Zr 90 Nb 94 Mo 96 Ru 104 Rh
104 Pd 106 Ag 108 Cd 112 In
113 Sn 118 Sb 122
Te 125 I 127 Cs 133 Ba 137
Di 138 Ce 140 Er 178 La 180
Ta 182 W 184 Os 195 Ir 197
Pt 198 Au 199 Hg 200 Tl 204
Pb 207 Bi 208 Th 231 U 240
Atomic Weights (Berzelius*)
*Recalculated using Cannizzaro’s principle

Ca = 40 Sr = 87 Ba = 137
(40+137)/2 = 88.5
Cl = 35.5 Br = 80 I = 127
(35.5+127)/2 = 81.2
K = 39 Rb = 85 Cs = 133
(39+133)/2 = 86
S = 32 Se = 78 Te = 125
(32+125)/2 = 78.5
P = 31 As = 75 Sb = 122
(31+122)/2 = 76.5
“Triads” suggest an underlying pattern
Johann Döbereiner
Jena, Germany
1829

The Chemical Congress of 1860
The time had come for chemists to resolve several questions and
to come to agreement on several conventions.
While Lincoln was debating key issues during the
Presidential campaign in the fall of 1860, chemists
from all over the world congregated in Karlsruhe.
Ständehaus, Karlsruhe, Germany

Chemical formula symbols were particularly confusing; various
conventions were in use, utilizing bars, dots, sometimes
equivalents and sometimes weights. H2O2 could represent either
water or hydrogen peroxide, C2H4 either ethylene or methane!
The Chemical Congress debated
several key issues. Foremost were
(1) the question of whether to use
chemical equivalents (the amount
of an element that reacts with a
standard weight of oxygen) or
atomic weights to describe
chemical reactions, and (2) what
symbolism to use for chemical
formulas.

Cannizzaro provides the solution
Stanislao Cannizzaro wrote a famous pamphlet which was
distributed at the Chemical Congress which clearly distinguished
between atoms and molecules and allowed an unequivocal
working definition of atomic weight. Almost immediately
everyone was converted to his system, which we use today.
Cannizzaro based his suggestions on Avogadro’s hypothesis.

Avogadro’s hypothesis is “rediscovered”
Amedeo Avogadro was far ahead of his time when he published
in 1811 his hypothesis that equal volumes of all gases contain equal
numbers of molecules (at the same temperature and pressure).
Cannizzaro showed that application of Avogadro’s hypothesis
produced a self-consistent set of atomic weights.
Cannizzaro “rediscovered”
Avogadro’s work on gas
volumes which had been
ignored for half a century.

A word more about volumes of gases. . .
Gay-Lussac had found in 1808 that when gases
chemically react, the volumes of both the reactants
and the products are in simple ratios. For example,
1 volume nitrogen + 3 volumes hydrogen
react to give 2 volumes of ammonia.
Avogadro interpreted this reaction as expressing
what happens on an atomic (and molecular) scale,
by borrowing from Dalton’s atomic theory:
N H H H+ Am Am

And a final word about water. . .
Avogadro in 1811 actually hypothesized the
correct interpretation in the reaction of
hydrogen with oxygen to produce water.
Again, Avogadro explained this reaction as
expressing what happens on an atomic (and
molecular) scale, using Dalton’s atomic theory:
O H H+ Wa Wa

Another kind of information which helped
Cannizzaro was Dulong-Petit’s law, which was
useful for solids. It stated that the gram atomic
heat capacity is constant. That is, the specific
heat (heat required to warm a substance by one
degree) is inversely to the atomic weight.
sp. heat at. wt. sp. ht. x at. wt.
(O=1)
Bi 0.0288 13.30 0.3830
Pb 0.0293 12.95 0.3794
Au 0.0298 12.43 0.3704
Pt 0.0314 11.16 0.3740
Sn 0.0514 7.35 0.3779
Ag 0.0557 6.75 0.3759
Zn 0.0927 4.03 0.3736
sp. heat at. wt. sp. ht. x at. wt.
(O=1)
Te 0.0912 4.03 0.3675
Cu 0.0949 3.957 0.3755
Ni 0.1035 3.69 0.3819
Fe 0.1100 3.392 0.3731
Co 0.1498 2.46 0.3685
S 0.1880 2.011 0.3780

The Cannizzaro Principle
The atomic weight of an element is the least weight of it
contained in a (volatile) molecule.
Hydrogen, the lightest gas, is chosen as the standard,
and the atomic weight of hydrogen is set at 1.
Since the molecule of hydrogen weighs twice as much as the
least amount in various compounds (e.g., HCl), then the
molecule of hydrogen contains two atoms, and its chemical
formula may be set as H2. Since two volumes of hydrogen
react with one volume of oxygen to give two volumes of
water, then it may be unequivocally concluded that
2H2 + O2 2H2O

“I well remember how great was the difference
of opinion, and how a compromise was advocated
with great acumen by many scientific men. . . .
In the spirit of freedom. . . A compromise was
not arrived at, nor ought it to have been,
but instead the truth. . . [which] soon afterwards
convinced all minds.” — Dmitri Mendeleev
“. . . The scales fell from my eyes, doubts
vanished, and a feeling of calm certainty
came in their place.” — Lothar Meyer
The two future discoverers of the Periodic Table, after reading
Cannizzaro’s Pamphlet at the Chemical Congress, stated:

The Discovery of the Modern Periodic Table
Lothar Meyer Dimitri Mendeleev
Two scientists independently discovered
the “modern” Periodic Table in 1869.

Mendeleév on his desk played and arranged pieces of paper,
listing elements with their respective atomic weights,
trying to find some order.
Dimitri Mendeleév
St. Petersburg,
Russia

Mendeleev’s First Table — March, 1869
Ti 50 Zr 90 ?100
V 51 Nb 94 Ta 182
Cr 52 Mo 96 W 186
Mn 55 Rh 104.4 Pt 197.4
Fe 56 Ru 104.4 Ir 198
Ni=Co 59 Pd 106.6 Os 199
H 1 Cu 63.4 Ag 108 Hg 200
Be 9.4 Mg 24 Zn 65.2 Cd 112
B 11 Al 27.4 ? 68 U 116 Au 197?
C 12 Si 28 ? 70 Sn 118
N 14 P 31 As 75 Sb 122 Bi 210?
O 16 S 32 Se 79.4 Te 128?
F 19 Cl 35.5 Br 80 I 127
Li 7 Na 23 K 39 Rb 85.4 Cs 133 Tl 204
Ca 40 Sr 87.6 Ba 137 Pb 207
? 45 Ce 92
Er? 56 La 94
Yt? 60 Di 95
In 75.6? Th 118?

1. When arranged by atomic weight, the elements show a
periodicity of properties.
2. Similar elements have atomic weights which are either very
similar (platinum, iridium, osmium) or which increase regularly
(potassium, rubidium, cesium).
3. The arrangement of the elements correspond to their valences.
4. Elements which are most common have small atomic weights.
5. The atomic weight can determine the character of an element.
6. More elements will be discovered.
7. The atomic weight of an element may be corrected by
comparison with adjacent elements.
8. Some properties of unknown elements can be predicted from
their atomic weights.
Mendeleev made 8 statements about his
Table in his first publication

Lothar Meyer’s Table — December, 1869
I II III IV V VI VII VIII IX
B 11 Al 27.3 — — ? In 113.4 Tl
202.7
C 11.97 Si 28 — Sn 117.8 — Pb
206.4
Ti 48 Zr 89.7
N 14.01 P 30.9 As 74.9 Sb 122.1 Bi 207.5
V 51.2 Nb 93.7 Ta 182.2
O 15.96 S 31.98 Se 78.0 Te 128?
Cr 52.4 Mo 95.6 W 183.5
F 19.1 Cl 35.38 Br 79.75 I 126.5
Mn 54.8 Ru 103.5 Os 198.6?
Fe 55.9 Rh 104.1 Ir 196.7
Co&Ni 58.6 Pd 106.2 Pt 196.7
Li 7.01 Na 22.99 K 39.04 Rb 85.2 Cs 132.7
Cu 63.3 Ag 107.66 Au 196.2
?Be 9.7 Mg 23.9 Ca39.9 Sr 87.0 Ba 136.8
Zn 64.9 Cd 111.6 Hg 199.8

Lothar Meyer’s plot
Atomic weight
Atomicvolume
Lothar Meyer’s plot shows definite spikes in an ascending cyclic
pattern that suggests an internal structure. The intriguing
question of atomic structure had to wait for another half century,
until spectroscopists and theoreticians could attack the problem.

Differences between Mendeleev and Meyer
1. Mendeleev did not concern himself with why the table worked.
He just boldly proclaimed that the trends were real, and that
in fact the properties of unknown elements could be predicted!
2. Meyer was not so daring about the predictive power of the
table. He was very curious, however, with the reasons for the
trends, which he thought reflected some internal structure.
3. Mendeleev thought the elements were primordial matter.
4. Meyer thought there must be yet smaller particles.
5. Mendeleev continued to work on his table, which very
quickly was successful in predicting specific elements —
and he became famous.
6. It took scientists many decades understand exactly how
Meyer’s plot described an inner structure of the atom, and
his work was eclipsed by these scientists who discovered this
structure of protons, electrons, and neutrons.

PERIODIC TABLE OF THE ELEMENTS
(Mendeléeff, 1871)
Row 1
R2O
2
RO
3
R2O3
4
RO2
RH4
5
R2O5
RH3
6
RO3
RH2
7
R2O7
RH
8
RO4
1
H
1
  
2 Li
7
Be
9.4
B
11
C
12
N
14
O
16
F
19
3 Na
23
Mg
24
Al
27.
3)
Si
28
P
31
S
32
Cl
35.
5)
4 K
39
Ca
40
"eka-
B"
44?
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
5 Cu
63
Zn
65
"eka-
Al"
68?
"eka-
Si"
72?
As
75
Se
78
Br
80
6
Rb
85
Sr
87
Y
88
Zr
90
Nb
94
Mo
96 100
?)
Ru
104
)
Rh
104
)
Pd
106
)
7
Ag
108
)
Cd
112
)
In
113
)
Sn
118
)
Sb
122
)
Te
125
)
I
127
)
8
Cs
133
)
Ba
137
)
Di
138
)
Ce
140
)
9
10
Er
178
)
La
180
)
Ta
182
)
W
184
)
Os
195
)
Ir
197
)
Pt
198
)
11 Au
199
)
Hg
200
)
Tl
204
)
Pb
207
)
Bi
208
)
12 Th
231
)
U
240
)
Mendeléeff assumed: oxide of Be = BeO
oxide of In = In2O3
oxide of U = UO3
? ?
? ?
? ?
?
Predicted!
Misfits?
Correct
value?
eka-boron
eka-aluminum
eka-silicon

Mendeleev simply followed the trends of the table to interpolate
the properties of three new elements, which he called eka-boron,
eka-aluminum, and eka-silicon. He predicted the atomic
weights would be 44, 68, and 72, respectively, and he predicted
the chemical properties and physical properties of each of these
elements.
His paper didn’t get much attention until. . . .
How Mendeleev predicted unknown elements
Eka-B
44
Eka-Al
68
Eka-Si
72

Gallium - discovered 1875
Boisbaudran discovers eka-aluminum
Predicted Found
at. wt. = 68 at. wt. = 69.9
sp. gr. = 5.9 sp. gr. = 5.94
low m.p. m.p. = 30º
Oxide Ea2O3 Oxide Ga2O3
soluble in acids soluble in acids
and bases and bases
Lecoq
de Boisbaudran,
Cognac, France

Scandium - discovered 1879
Nilson discovers eka-boron
Predicted Found
at. wt. = 44 at. wt. = 44
Oxide Eb2O3 Oxide Sc2O3
with sp. gr. = with sp.gr. =
3.5, not soluble 3.86, not soluble
in alkalies in alkalies
Lars Fredrik Nilson,
Uppsala, Sweden

Germanium - discovered 1886
Winkler discovers eka-silicon
Predicted Found
at. wt. = 72 at. wt. = 72.3
Oxide EsO2 Oxide GeO2
with sp. gr. = with sp. gr. =
4.7 4.70
Volatile chloride GeCl4 with
EsCl4 b.p. = 86 º
Clemens Winkler,
Freiberg, Germany

(Mendeléeff, 1891)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7
R2O RO R2O3 RO2 R2O5 RO3 R2O7 R2O RO R2O3 RO2 R2O5 RO3 R2O7
   H
1
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
)
K
39
Ca
40
Sc
44
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
58.
5)
Ni
59
Cu
63
Zn
65
Ga
70
Ge
72
As
75
Se
79
Br
80
Rb
85
Sr
87
Y
89
Zr
90
Nb
94
Mo
96
Ru
103
)
Rh
104
)
Pd
106
)
Ag
108
)
Cd
112
)
In
113
)
Sn
118
)
Sb
120
)
Te
125
)
I
127
)Cs
133
)
Ba
137
)
La
138
)
Ce
140
)Yb
173
)
Ta
182
)
W
184
)
Os
191
)
Ir
193
)
Pt
196
)
Au
198
)
Hg
200
)
Tl
294
)
Pb
206
)
Bi
208
)Th
232
)
U
240
)
Also known in 1891: Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, Dy
Difficulties include: Brauner found Te = 127.6 1889

A new family of elements?!
Sir William Ramsey
University College
(London)
New gas
isolated from
the atmosphere!

(1894)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7
   H
1
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
)
Ar
40
K
39
Ca
40
Sc
45
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
Cu
63
Zn
65
Ga
70
Ge
73
As
75
Se
79
Br
80
Rb
85
Sr
88
Y
89
Zr
91
Nb
93
Mo
96
Ru
101
Rh
104
Pd
106
Ag
108
Cd
112
In
115
Sn
119
Sb
122
Te
128
I
127
Cs
133
Ba
137
La
139
Ce
140
Yb
173
Ta
181
W
184
Os
190
Ir
192
Pt
195
Au
197
Hg
201
Tl
204
Pb
207
Bi
209
Th
232
U
238
Also known in 1894: Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, Dy
A new column is needed for the new element!

(1895)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7
   H
1
He
4
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
)
Ar
40
K
39
Ca
40
Sc
45
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
Cu
63
Zn
65
Ga
70
Ge
73
As
75
Se
79
Br
80
Rb
85
Sr
88
Y
89
Zr
91
Nb
93
Mo
96
Ru
101
Rh
104
Pd
106
Ag
108
Cd
112
In
115
Sn
119
Sb
122
Te
128
I
127
Cs
133
Ba
137
La
139
Ce
140
Yb
173
Ta
181
W
184
Os
190
Ir
192
Pt
195
Au
197
Hg
201
Tl
204
Pb
207
Bi
209
Th
232
U
238
Also known in 1895: Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, DyAnother gas discovered! (was originally seen in the sun)

(1898)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7
   H
1
He
4
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
)
Ar
40
K
39
Ca
40
Sc
45
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
Cu
63
Zn
65
Ga
70
Ge
73
As
75
Se
79
Br
80
Kr
84
Rb
85
Sr
88
Y
89
Zr
91
Nb
93
Mo
96
Ru
101
Rh
104
Pd
106
Ag
108
Cd
112
In
115
Sn
119
Sb
122
Te
128
I
127
Xe
131
Cs
133
Ba
137
La
139
Ce
140
Yb
173
Ta
181
W
184
Os
190
Ir
192
Pt
195
Au
197
Hg
201
Tl
204
Pb
207
Bi
209
Th
232
U
238
Also known in 1898: Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, DyTwo more gases discovered!

(1898)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7
   H
1
He
4
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
Ne
20
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
)
Ar
40
K
39
Ca
40
Sc
45
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
Cu
63
Zn
65
Ga
70
Ge
73
As
75
Se
79
Br
80
Kr
84
Rb
85
Sr
88
Y
89
Zr
91
Nb
93
Mo
96
Ru
101
Rh
104
Pd
106
Ag
108
Cd
112
In
115
Sn
119
Sb
122
Te
128
I
127
Xe
131
Cs
133
Ba
137
La
139
Ce
140
Yb
173
Ta
181
W
184
Os
190
Ir
192
Pt
195
Au
197
Hg
201
Tl
204
Pb
207
Bi
209
Th
232
U
238
Also known in 1898: Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, DyAnother gas discovered ! (Table needs to be restacked)

Mendeléeff's Last Periodic Table
(1902)
Ro
w
0
R
1
R2O
2
RO
3
R2O3
4
RO2
5
R2O5
6
RO3
7
R2O7
8
RO4
1 H
1.008
2 He
4.0
Li
7.03
Be
9.1
B
11.0
C
12.0
N
14.0
4
O
16.0
0
F
19.0
3 Ne
19.9
Na
23.0
5
Mg
24.3
Al
27.0
Si
28.4
P
31.0
S
32.0
6
Cl
35.4
5
4 Ar
38
K
39.1
Ca
40.1
Sc
44.1
Ti
48.1
V
51.4
Cr
52.1
Mn
55.0
Fe
55.9
Co
59
Ni
59
5 Cu
63.6
Zn
65.4
Ga
70
Ge
72.3
As
75
Se
79
Br
79.9
5
6 Kr
81.8
Rb
85.4
Sr
87.6
Y
89.0
Zr
90.6
Nb
94.0
Mo
96.0
Ru
101.7
Rh
103.0
Pd
106.5
7 Ag
107.9
Cd
112.4
In
114.0
Sn
119.0
Sb
120.0
Te
127
I
127
8 Xe
128
Cs
132.9
Ba
137.4
La
139
Ce
140
9
10 Yb
173
Ta
183
W
184
Os
191
Ir
193
Pt
194.9
11 Au
197.2
Hg
200.0
Tl
204.1
Pb
206.9
Bi
208
12 Ra
224
Th
232
U
239
Not included:
Er, Tb, Ho, Tm, Sm, Gd, Pr, Nd, Dy, Eu, Po, Ac, Rn

(Brauner, 1902)
Row 0
R
1
R2O
2
RO
3
R2O3
4
RO2
RH4
5
R2O5
RH3
6
RO3
RH2
7
R2O7
RH
8
RO4
1 H
1
  
2 He
4
Li
7
Be
9
B
11
C
12
N
14
O
16
F
19
3 Ne
20
Na
23
Mg
24
Al
27
Si
28
P
31
S
32
Cl
35.5
4 Ar
40
K
39
Ca
40
Sc
44
Ti
48
V
51
Cr
52
Mn
55
Fe
56
Co
59
Ni
59
5 Cu
63
Zn
65
Ga
70
Ge
72
As
75
Se
78
Br
80
6 Kr
82
Rb
85
Sr
87
Y
89
Zr
90
Nb
94
Mo
96 100
Ru
102
Rh
103
Pd
106
7 Ag
108
Cd
112
In
114
Sn
119
Sb
120
Te
128
I
127
8 Xe
128
Cs
133
Ba
137
La
139
Ce
140
Pr
141
Nd
144 145
147
Sm
148
Eu
151 152
155
Gd
156 159 160
Tb
163
Ho
165
Er
166 167
Tm
171
Yb
173 176
178
Ta
182
W
184 190
Os
191
Ir
193
Pt
195
9 Au
197
Hg
200
Tl
204
Pb
207
Bi
209 212 214
10
218 220
Ra
225 230
Th
233 235
U
239
Not included: Dy, Po, Ac, Rn
Predicted?!
Bauner
predicted 98
elements
through
uranium
Brauner
attempted to
find order in
the higher
elements
Bohuslav Brauner
Prague, Bohemia

A further complication — Rutherford
discovers the “transmutation” of elements
In 1902-1905 Ernest Rutherford discovered that
radium decays through a series of steps, leading
apparently to a new group of elements:
Ra
Rn Ra-A Ra-B Ra-C

A glut of new elements?!
Rutherford’s finding led to the discoveries by other
invesigators of a plethora of new elements in other decay
schemes during the first decade of 1900. These elements
included: “ionium,” “brevium,” “actinouranium,”
“radiothorium,” “niton,” “actinon,” “thorium-X,”
“uranium-X,” and dozens more.
The confusing feature of all these newly discovered
elements was that in many instances some of them had
very similar, and perhaps identical, chemical properties
— even though they had different half-lives.

Soddy solves the problem
In 1913 Soddy conceived the idea of an “isotope.” Isotopes (from
Greek “isos” meaning “same,” and “topos” meaning “place”) are
“in the same place” in the Periodic Table and yet have different
nuclear properties. Thus, for example, the “brevium” of Fajans,
the “ekatantalum” of Soddy, and the “protactinium” of Hahn and
Meitner all belong in the same slot in the Periodic Table — they
are isotopes of the same element (protactinium).

(1907)
1A 2A 3B 4B 5B 6B 7B 8B 1B 2B 3A 4A 5A 6A 7A 8A
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba Rare earths
Ta W Os Ir Pt Au Hg Tl Pb Bi Po Rn
Ac Th U
Rare earths: La, Ce, Er, Tb, Ho, Tm, Yb, Sm, Gd, Pr, Nd, Dy, Eu, Lu
This was the best guess by 1907 — but it was still not
known how many elements actually existed. . . . until. . . . .

1-N=
4
3
0ν
ν
Moseley — 1912
Where N = atomic number
of element
v = 1/λ = wavenumber of Kα
X-ray line
v0 = Rydberg constant
Henry Moseley
Oxford, England

Moseley predicted the following
elements were yet to be discovered:
43, 61, 75, 85, 87
From Moseley’s work, scientists now knew that
there were exactly 92 elements ranging from
hydrogen to uranium.
And using quantum theory, Bohr was ready to
propose the modern form of the Periodic Table. . . .

(1925)
H He
Li Be B C N O F Ne
Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po Rn
Ra Ac Th Pa U
* Rare earths

Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
 Bohr explained behavior of transition elements and rare-earth elements in 1922.
 Hafnium was discovered in zirconium ore after Bohr's suggestion that the missing
element would behave more like zirconium than like a rare earth element.
 Rhenium was discovered from platinum ores.
 "Masurium" (eka-manganese) was announced but later discredited.
 "Illinium" (the missing rare earth) was announced but later discredited.
Niels Bohr
Copenhagen, Denmark

1939
1940
1937
Only one left to be discovered!
Glenn Seaborg
Berkeley, California
(1940)
H He
Li Be B C N O F Ne
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac*
** Lanthanides

Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
* * Actinides

Th Pa U
Seaborg suggested transuranium elements were a new series, akin to the rare earths.
Seaborg recommended the names "lanthanides" and "actinides" for these series.

(1948)
H He
Li Be B C N O F Ne
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac*
** Lanthanides

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
* * Actinides

Th Pa U Np Pu Am
Promethium was discovered in an atomic pile
in Oak Ridge, Tennessee (1945)
And the transuranium elements were
discovered by Seaborg and others. . . .

History of periodic table part 3 - copy

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