ATOMIC PROPERTIES ASSOCIATED WITH THE NUCLEUS
The properties determined by the atomic nucleus are the mass, and the isotopic and radioactive properties. The astrophysical study of these factors is as yet in an elementary stage, but it seems that all three have a bearing on the frequency of atomic species, and that future theory may also relate them to the problem of the source and fate of stellar energy. Moreover, up to the present no general formulation of the theory of the formation and stability of the elements has been possible, and it is well to keep in mind the data which are apparently most relevant to the problem—the observational facts relating to the nucleus. Probably the study of the nucleus involves the most fundamental of all cosmical problems—a problem, moreover, which is largely in the hands of the laboratory physicist.
The chief nuclear data are summarized in Table I. Successive columns contain the atomic number, the element and its chemical symbol, the atomic weight[1] and the mass numbers of the known isotopes,[2] the percentage terrestrial abundance,[3] expressed in atoms, and the recorded stellar occurrence. Presence in the stars is indicated by an asterisk, absence by a dash.
[TABLE I]
| No. | Element | Atomic Weight | Isotopes | Percentage Terrestrial Abundance (Atoms) | Stellar Occurrences | |
|---|---|---|---|---|---|---|
| 1 | Hydrogen | H | 1.008 | 1.008 | 15.459 | * |
| 2 | Helium | He | 4.00 | 4 | .. | * |
| 3 | Lithium | Li | 6.94 | 7, 6 | 0.0129 | * |
| 4 | Beryllium | Be | 9.01 | 9 | 0.0020 | — |
| 5 | Boron | B | 11.0 | 11, 10 | 0.0016 | — |
| 6 | Carbon | C | 12.005 | 12 | 0.2069 | * |
| 7 | Nitrogen | N | 14.01 | 14 | 0.0383 | * |
| 8 | Oxygen | O | 16.00 | 16 | 59.940 | * |
| 9 | Fluorine | F | 19.0 | 19 | 0.0282 | — |
| 10 | Neon | Ne | 20.0 | 20, 22, (21) | .. | — |
| 11 | Sodium | Na | 23.00 | 23 | 2.028 | * |
| 12 | Magnesium | Mg | 24.32 | 24, 25, 26 | 1.426 | * |
| 13 | Aluminium | Al | 27.1 | 4.946 | * | |
| 14 | Silicon | Si | 28.3 | 28, 29, 30 | 16.235 | * |
| 15 | Phosphorus | P | 31.04 | 31 | 0.0818 | — |
| 16 | Sulphur | S | 32.06 | 32 | 0.0518 | * |
| 17 | Chlorine | Cl | 35.46 | 35, 37, (39) | 0.1149 | — |
| 18 | Argon | A | 39.88 | 40, 36 | .. | — |
| 19 | Potassium | K | 39.10 | 39, 41 | 1.088 | * |
| 20 | Calcium | Ca | 40.07 | (40, 44) | 1.503 | * |
| 21 | Scandium | Sc | 44.1 | 45 | .. | * |
| 22 | Titanium | Ti | 48.1 | 48 | 0.2407 | * |
| 23 | Vanadium | V | 51.0 | 51 | 0.0133 | * |
| 24 | Chromium | Cr | 52.0 | 52 | 0.0213 | * |
| 25 | Manganese | Mn | 54.93 | 55 | 0.0351 | * |
| 26 | Iron | Fe | 55.84 | 54, 56 | 1.485 | * |
| 27 | Cobalt | Co | 58.97 | 59 | 0.0009 | * |
| 28 | Nickel | Ni | 58.68 | 58, 60 | 0.0091 | * |
| 29 | Copper | Cu | 63.57 | 63, 65 | 0.0028 | * |
| 30 | Zinc | Zn | 65.37 | (64, 66, 68, 70) | 0.0011 | * |
| 31 | Gallium | Ga | 69.9 | 69, 71 | .. | — |
| 32 | Germanium | Ge | 72.5 | 74, 72, 70 | .. | — |
| 33 | Arsenic | As | 74.96 | 75 | .. | — |
| 34 | Selenium | Se | 79.2 | .. | — | |
| 35 | Bromine | Br | 79.92 | 79, 81 | .. | — |
| 36 | Krypton | Kr | 82.92 | 84, 86, 82, 83, 70, 78 | .. | — |
| 37 | Rubidium | Rb | 85.45 | 85, 87 | .. | * |
| 38 | Strontium | Sr | 87.63 | 88, 86 | 0.0065 | * |
| 39 | Yttrium | Y | 88.7 | 89 | 0.0030 (with Ce) | * |
| 40 | Zirconium | Z | 90.6 | 90, 92, 94 | 0.0095 | * |
| 41 | Niobium | Nb | 93.1 | .. | ? | |
| 42 | Molybdenum | Mo | 96 | .. | * | |
| 43 | .. | .. | .. | |||
| 44 | Ruthenium | Ru | 101.7 | .. | * | |
| 45 | Rhodium | Rh | 102.9 | .. | * | |
| 46 | Palladium | Pd | 106.7 | .. | * | |
| 47 | Silver | Ag | 107.88 | 107, 109 | .. | * |
| 48 | Cadmium | Cd | 112.40 | 110, 111, 112, 113, 114, 116 | .. | — |
| 49 | Indium | In | 114.8 | .. | — | |
| 50 | Tin | Sn | 118.7 | .. | ? | |
| 51 | Antimony | Sb | 120.2 | .. | — | |
| 52 | Tellurium | Te | 127.5 | 126, 128, 130 | .. | — |
| 53 | Iodine | I | 126.92 | 127 | .. | — |
| 54 | Xenon | Xe | 130.2 | 129, 132, 131, 134, 136, (128, 130) | .. | — |
| 55 | Caesium | Cs | 132.81 | 133 | .. | * |
| 56 | Barium | Ba | 137.37 | 138 | 0.0098 | * |
| 57 | Lanthanum | La | 139.0 | 139 | .. | * |
| 58 | Cerium | Ce | 140.25 | 140, 142 | 0.0030 (with Y) | * |
| 59 | Praseodymium | Pr | 140.9 | 141 | .. | — |
| 60 | Neodymium | Nd | 144.3 | 142-150 | .. | — |
| 61 | .. | .. | .. | .. | ||
| 62 | Samarium | Sa | 150.4 | .. | — | |
| 63 | Europium | Eu | 152.0 | .. | * | |
| 64 | Gadolinium | Gd | 157.3 | .. | — | |
| 65 | Terbium | Tb | 159.2 | .. | * | |
| 66 | Dysprosium | Dy | 162.5 | .. | — | |
| 67 | Holmium | Ho | 163.5 | .. | — | |
| 68 | Erbium | Er | 167.7 | .. | — | |
| 69 | Thulium | Tm | 168.5 | .. | — | |
| 70 | Ytterbium | Yb | 173.5 | .. | — | |
| 71 | Lutecium | Lu | 175.0 | .. | — | |
| 72 | Hafnium | Hf | .. | — | ||
| 73 | Tantalum | Ta | 181.5 | .. | — | |
| 74 | Tungsten | W | 184.0 | .. | — | |
| 75 | .. | .. | — | |||
| 76 | Osmium | Os | 190.9 | .. | — | |
| 77 | Iridium | Ir | 193.1 | .. | — | |
| 78 | Platinum | Pt | 195.2 | .. | — | |
| 79 | Gold | Au | 197.2 | .. | — | |
| 80 | Mercury | Hg | 200.6 | (197, 198, 199, 200) 202, 204 | .. | — |
| 81 | Thallium | Tl | 204.0 | .. | — | |
| 82 | Lead | Pb | 207.2 | 0.0002 | * | |
| 83 | Bismuth | Bi | 208.0 | .. | — | |
| 84 | .. | .. | .. | .. | ||
| 85 | .. | .. | .. | .. | ||
| 86 | Radon | Rd | 222.4 | .. | — | |
| 87 | .. | .. | .. | .. | ||
| 88 | Radium | Ra | 226.0 | .. | — | |
| 89 | .. | .. | .. | .. | ||
| 90 | Thorium | Th | 232.4 | .. | — | |
| 91 | .. | .. | .. | .. | ||
| 92 | Uranium | U | 238.2 | .. | — | |
ARRANGEMENT OF EXTRA-NUCLEAR ELECTRONS
Logically a description of the analysis of spectra should precede the discussion of electron arrangement, for our knowledge of the extra-nuclear electrons is very largely based on spectroscopic evidence. The established conceptions of atomic structure, however, are useful in classifying mentally the general outlines of the origin of line spectra, and therefore, for convenience of reference, Bohr’s table[4] of the arrangement of extra-nuclear electrons is here prefixed to our brief discussion of spectroscopic data. The chemical elements are given in order of atomic number, and successive columns contain, for the atom in its normal state, the numbers of electrons in the various quantum orbits.
Figure 1
Arrangement of electron orbits for the atom of neutral sodium. Orbits consisting partly of broken lines are circular orbits seen in perspective. The numbers and quantum relations of the orbits are as follows: inner shell, two