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3.1.2 Properties of the elements
Symbols, atomic weights, atomic
numbers, densities, melting points and boiling points (pressure 101.325 kN
m−2) of the elements
The values of the relative atomic masses
(Ar(E)), scaled to the relative mass
Ar(12C) = 12, are those recommended in the 1991
Report by the International Union of Pure and Applied Chemistry Commission on
Atomic Weights (IUPAC, 1992). The regular biennial reviews by the Commission
rely on significant improvements in the precision of mass measurement and
refined assessment of isotopic composition of terrestrial materials. (Separate
tables of information on the composition and relative mass for
extra-terrestrial sources are presented in the Commission Reports.)
In the following table of the elements, arranged in
alphabetical order, uncertainty in the last reported digit is expressed as
‘± n’. Precision has improved significantly in the
past 15 years. The biennial reports for 1979 to 1991 present one or more
improvements for 66 elements, and although the uncertainty still remains in
excess of 0.01% for 24 elements, many of these suffer
from variable isotopic composition. Typical improvements recorded in the 1989
report (IUPAC, 1991) include tightening the Ar of Ni from
58.69 to 58.6934 ± 2 and of Sb from 121.75 to 121.757 ± 3, while
better knowledge of isotopic composition reduced the uncertainty for Hg so that
Ar became 200.59 ± 2, and 231Pa was fixed
at 231.035 88 ± 2. The 1991 report (IUPAC, 1992) took advantage of
higher precision mass measurement to tighten In to 114.818 ± 3, W to
183.84 ±1 and Os to 190.23 ± 3. The footnote symbol
‘g’, which reflects the detection of variable abundance
in some terrestrial geological specimens (see the notes at the foot of the
table), was added for C and K. The footnotes to this table elaborate the types
of variations to be expected for individual elements. The values of
Ar(E) given here apply to elements as they exist naturally on
earth. When used with due regard to the footnotes they are considered reliable
to ± 1 in the last digit unless otherwise noted. An element with an
asterisk has no stable isotope and lacks a characteristic terrestrial isotopic
composition. A value in parenthesis is the atomic weight of the isotope of the
radionuclide of that element which is believed to be the most frequently found
and which has the longest half-life.
For a discussion of the arrangement of electrons in
atoms, and a table (in atomic number order) of the electron
configuration of elements for the ground state of neutral atoms, see
Section 4.1.1. For a table listing one or more
ionisation potentials for elements from Hydrogen to Lanthanum (Z = 57)
and some commoner atoms of higher Z,
see
Section 4.1.2.
|
Element
|
Symbol
|
Atomic
No. |
Atomic
weight |
|
|
|
|
|
|
|
|
|
|
|
|
Actinium* |
Ac |
89 |
(227.027
8) |
10 060 |
1050 |
3200 |
|
Aluminium |
Al |
13 |
26.981 539 ± 5 |
2 698 |
660.323† |
2520 |
|
Americium* |
Am |
95 |
(243.061
4) |
13 670 |
1176 |
2600 |
|
Antimony |
Sb |
51 |
121.757 ± 3 |
6 692 |
630.63† |
1587 |
|
Argon |
Ar |
18 |
39.948g, r |
1656/ − 233 °C |
–189.34 |
–185.856† |
|
Arsenic |
As |
33 |
74.921 59 ± 2 |
5 776 |
610 solid sublimes |
|
Astatine* |
At |
85 |
(209.987
1) |
|
300 |
350 |
|
Barium |
Ba |
56 |
137.327 ± 7g |
3 594 |
728 |
1900 |
|
Berkelium* |
Bk |
97 |
(247.070
3) |
14 790 |
1050 |
|
|
Beryllium |
Be |
4 |
9.012 182 ± 3 |
1 846 |
1287 |
2470 |
|
Bismuth |
Bi |
83 |
208.980 37 ± 3 |
9 803 |
271.442† |
1560 |
|
Boron |
B |
5 |
10.811 ± 5m, r |
2 466 |
2075 |
4000 |
|
Bromine |
Br |
35 |
79.904 |
3 120 |
–7.3 |
58.9 |
|
Cadmium |
Cd |
48 |
112.411 ±
8g |
8 647 |
321.08† |
770 |
|
Caesium |
Cs |
55 |
132.905 43 ± 5 |
1 900 |
28.4 |
670 |
|
Calcium |
Ca |
20 |
40.078 ±
4g |
1 530 |
840 |
1484 |
|
Californium* |
Cf |
98 |
(251.079
6) |
|
900 |
|
|
Carbon |
C |
6 |
12.011g.r |
2 266 |
4490 |
|
|
Cerium |
Ce |
58 |
140.115 ±
4 |
6 711 |
800 |
3420 |
|
Chlorine |
Cl |
17 |
35.4527 ± 9 |
2030/−160 °C |
−101 |
–34.0 |
|
Chromium |
Cr |
24 |
51.996 ± 6 |
7 194 |
1907 |
2670 |
|
Cobalt |
Co |
27 |
58.933 20 ±
1 |
8 800 |
1495† |
2930 |
|
Copper |
Cu |
29 |
63.546 ±
3r |
8 933 |
1084.62† |
2560 |
|
Curium* |
Cm |
96 |
(247.070
3) |
13 300 |
1345 |
|
|
Dysprosium |
Dy |
66 |
162.50 ±
3 |
8 531 |
1410 |
2560 |
|
Einsteinium* |
Es |
99 |
(252.081
6) |
|
860 |
|
|
Erbium |
Er |
68 |
167.26 ±
3g |
9 044 |
1530 |
2860 |
|
Europium |
Eu |
63 |
151.965 ±
9 |
5 248 |
822 |
1600 |
|
Fermium* |
Fm |
100 |
(257.095
1) |
|
1530 |
|
|
Fluorine |
F |
9 |
18.998 403 2 ±
9 |
1140/−200 °C |
−219.6 |
–188.1 |
|
Francium* |
Fr |
87 |
(223.018
5) |
|
27 |
650 |
|
Gadolinium |
Gd |
64 |
157.25 ±
3g |
7 870 |
1314 |
3260 |
|
Gallium |
Ga |
31 |
69.723 ± 1 |
5 905 |
29.76 |
2200 |
|
Germanium |
Ge |
32 |
72.61 ±
2 |
5 323 |
938 |
2830 |
|
Gold |
Au |
79 |
196.966 54 ±
3 |
19 281 |
1064.18† |
2850 |
|
Hafnium |
Hf |
72 |
178.49 ±
2 |
13 276 |
2230 |
4600 |
|
Helium |
He |
2 |
4.002 602 ±
2g, r |
120/4.22 K |
3–5
K‡ |
4.22
K |
|
Holmium |
Ho |
67 |
164.930 32 ±
3 |
8 797 |
1470 |
2700 |
|
Hydrogen |
H |
1 |
1.00794
± 7g, m, r |
89/- 266.8 °C |
− 259.35 |
-
252.87† |
|
Indium |
In |
49 |
114.818 ± 3 |
7 290 |
156.599† |
2070 |
|
Iodine |
I |
53 |
126.904 47 ± 3 |
4 953 |
113.6 |
184 |
|
Iridium |
Ir |
77 |
192.22 ±
3 |
22 550 |
2447† |
4430 |
|
Iron |
Fe |
26 |
55.847 ±
3 |
7 873 |
1540 |
2860 |
|
Krypton |
Kr |
36 |
83.80 ± 1g, m |
3000/−188 °C |
−157.3 |
–153.2 |
|
Lanthanum |
La |
57 |
138.905 5 ± 2g |
6 174 |
920 |
3460 |
|
Lawrencium* |
Lr |
103 |
(260.105
4) |
|
1630 |
|
|
Lead |
Pb |
82 |
207.2 ± 1g,
r |
11 343 |
327.502† |
1750 |
|
Lithium |
Li |
3 |
6.941 ± 2 g,
m, r |
533 |
180.5 |
1340 |
|
Lutetium |
Lu |
71 |
174.967 ± 1 |
9 842 |
1660 |
3390 |
|
Magnesium |
Mg |
12 |
24.305 0 ± 6 |
1 738 |
650 |
1090 |
|
Manganese |
Mn |
25 |
54.938 05 ± 1 |
7 473 |
1250 |
2060 |
|
Mendelevium* |
Md |
101 |
(258.098 6) |
|
830 |
|
|
Mercury |
Hg |
80 |
200.59 ± 2 |
13 546 |
−38.834† |
356.73† |
|
Molybdenum |
Mo |
42 |
95.94 ± 1 |
10 222 |
2623† |
4640 |
|
Neodymium |
Nd |
60 |
144.24 ±
3g |
7 000 |
1016 |
3070 |
|
Neon |
Ne |
10 |
20.179 7 ± 6g,
m |
1442/−268 °C |
−248.59 |
−246.08† |
|
Neptunium* |
Np |
93 |
(237.048 2) |
20 450 |
640 |
3900 |
|
Nickel |
Ni |
28 |
58.693 4 ± 2 |
8 907 |
1455† |
2990 |
|
Niobium |
Nb |
41 |
92.906 38 ± 2 |
8 578 |
2477† |
4700 |
|
Nitrogen |
N |
7 |
14.006 74 ±
7g |
1035/−268.8 °C |
−210 |
−195.80† |
|
Nobelium* |
No |
102 |
(259.100 9) |
|
830 |
|
|
Osmium |
Os |
76 |
190.23 ± 3g |
22 580 |
3030 |
5000 |
|
Oxygen |
O |
8 |
15.999 4 ± 3g,
r |
1460/−252.7 °C |
−
218.79† |
−182.96† |
|
Palladium |
Pd |
46 |
106.42 ± 1g |
11 995 |
1555† |
2960 |
|
Phosphorus |
P |
15 |
30.973 762 ± 4 |
1820 (yellow) |
44.2 (yellow) |
277 |
|
Platinum |
Pt |
78 |
195.08 ± 3 |
21 450 |
1768† |
3820 |
|
Plutonium* |
Pu |
94 |
(244.064 2) |
19 814 |
640 |
3230 |
|
Polonium* |
Po |
84 |
(208.982 4) |
9 400 |
254 |
960 |
|
Potassium |
K |
19 |
39.098 3 ± 1 |
862 |
63.4 |
760 |
|
Praseodymium |
Pr |
59 |
140.907 65 ± 3 |
6 779 |
931 |
3510 |
|
Promethium* |
Pm |
61 |
(144.912 7) |
7 220§ |
1142§ |
3300§ |
|
Protoactinium* |
Pa |
91 |
(231.035 88 ± 2) |
15 370 |
1570 |
4000 |
|
Radium* |
Ra |
88 |
(226.025
4) |
5 000 |
700 |
1500 |
|
Radon* |
Rn |
86 |
(222.017 6) |
440 (liquid |
−71 |
−62 |
|
|
|
|
|
–62 °C) |
|
|
|
Rhenium |
Re |
75 |
186.207 ± 1 |
21 023 |
3186 |
5600 |
|
Rhodium |
Rh |
45 |
102.905 50 ± 3 |
12 420 |
1963† |
3700 |
|
Rubidium |
Rb |
37 |
85.467 8 ± 3g |
1 533 |
39.3 |
690 |
|
Ruthenium |
Ru |
44 |
101.07 ±
2g |
12 360 |
2330 |
4150 |
|
Samarium |
Sm |
62 |
150.36 ±
3g |
7 536 |
1170 |
1790 |
|
Scandium |
Sc |
21 |
44.955 910 ± 9 |
2 992 |
1540 |
2830 |
|
Selenium |
Se |
34 |
78.96 ± 3 |
4 808 |
220 |
685 |
|
Silicon |
Si |
14 |
28.085 5 ± 3 |
2 329 |
1410 |
3260 |
|
Silver |
Ag |
47 |
107.868 2 ± 2g |
10 500 |
961.78† |
2160 |
|
Sodium |
Na |
11 |
22.989 768 ± 6 |
966 |
97.7 |
880 |
|
Strontium |
Sr |
38 |
87.62 ± 1g |
2 583 |
777 |
1380 |
|
Sulphur |
S |
16 |
32.066 ± 6r |
2 086 |
115.32 |
444.674† |
|
Tantalum |
Ta |
73 |
180.947 9 ± 1 |
16 670 |
3020 |
5560 |
|
Technetium* |
Tc |
43 |
(97.907 2) |
11 496 |
2160 |
4260 |
|
Tellurium |
Te |
52 |
127.60 ± 3g |
6 247 |
450 |
990 |
|
Terbium |
Tb |
65 |
158.925 34 ± 3 |
8 267 |
1360 |
3220 |
|
Thallium |
Tl |
81 |
204.383 3 ± 2 |
11 871 |
304 |
1470 |
|
Thorium* |
Th |
90 |
232.038 1 ± 1g,
x |
11 725 |
1750 |
4790 |
|
Thulium |
Tm |
69 |
168.934 21 ± 3 |
9 325 |
1550 |
1950 |
|
Tin |
Sn |
50 |
118.710 ± 7 |
7 285 |
231.928† |
2620 |
|
Titanium |
Ti |
22 |
47.88 ± 3 |
4 508 |
1670 |
3290 |
|
Tungsten |
W |
74 |
183.84 ± 1 |
19 254 |
3422† |
5550 |
|
Uranium* |
U |
92 |
238.028 9
± 1g, m, y |
19 050 |
1135 |
4130 |
|
Vanadium |
V |
23 |
50.941 5 ± 1 |
6 090 |
1920 |
3400 |
|
Xenon |
Xe |
54 |
131.29 ± 2g, m |
3560/(−185 °C) |
−111.8 |
−108.1 |
|
Ytterbium |
Yb |
70 |
173.04 ± 3 |
6 966 |
824 |
1200 |
|
Yttrium |
Y |
39 |
88.905 85 ±
2g |
4 475 |
1525 |
3340 |
|
Zinc |
Zn |
30 |
65.39 ± 2 |
7 135 |
419.527† |
910 |
|
Zirconium |
Zr |
40 |
91.224 ± 2g |
6 507 |
1850 |
4400 |
|
|
|
|
|
|
|
|
Notes:
The IUPAC Commission on Nomenclature of
Inorganic Chemistry (CNIC) provisional scheme (1978) of numerical names for
elements 104–107 (e.g. Un-nil-quadium for 104) has not been generally
popular. At its meeting in July 1994, CNIC proposed a sequence of names for
elements 104–109 which was confirmed by the IUPAC Bureau in September.
This CNIC set directly conflicted with the choice of names proposed by various
discoverers of these artificial elements at the JINR Dubna (Moscow), GSI
Darmstadt and Lawrence Berkeley (California) national laboratories and approved
in March 1994 by the American Chemical Society (ACS). The final decision to
uphold CNIC set (Dubnium, Joliotium, Rutherfordium, Bohrium, Hahnium and
Meitnerium respectively) or compromise with the ACS set (Rutherfordium,
Hahnium, Seaborgium, Neilsbohrium, Hassium and Meitnerium) has been deferred by
IUPAC Council until 1997.
|
g |
|
Geologically exceptional specimens are
known in which the element has an isotopic composition outside the limits for
normal material. The difference between the atomic weight of the element in
such specimens and that given in the table may considerably exceed the implied
uncertainty. |
|
m |
|
Modified isotopic compositions may be found
in commercially available material because it has been subjected to an
undisclosed or inadvertent isotopic separation. Substantial deviations in
atomic weight of the element from that given in the table can
occur. |
|
r |
|
Range in isotopic composition of normal
terrestrial material prevents a more precise atomic weight being given; the
tabulated A(E) value should be applicable to any normal
material.
|
|
x |
|
Thorium has a well defined (mononuclide) composition in
minerals with only rare exceptions. In certain places, however (most notably in
ocean water), measurable quantities of 230Th (Ionium) can be
found. |
|
y |
|
Uranium is the only element with no stable isotopes but
which has a characteristic terrestrial composition of long-lived isotopes
such that a meaningful atomic weight can be given for natural samples:
238U = 238.050 8. |
|
† |
|
Primary and secondary fixed points on the International
Practical Temperature Scale of 1990. |
|
‡ |
|
This and other values marked K are in
kelvins. |
|
§ |
|
This property refers to 147Pm. |
References
IUPAC (1991) Pure & Appl. Chem., 63,
976–1002.
IUPAC (1992) Pure & Appl. Chem., 64,
1519–1534.
G.F.Phillips
|
|
