Chemistry · Ch 3 — Periodic Classification of Elements
Mendeleev's Classification
Mendeleev's Classification
Lothar Meyer's contribution (1868). Around the same time as Mendeleev, Julius Lothar Meyer built a table of the elements that closely resembles the modern one. He plotted physical properties -- atomic volume, melting point, boiling point -- against atomic weight and noticed the same periodic pattern Mendeleev would describe algebraically.
Mendeleev's Periodic Law. Dmitri Mendeleev independently proposed that "the properties of the elements are the periodic functions of their atomic weights." Arranging the 70 elements known at the time in order of increasing atomic weight, he placed them into vertical columns (groups, labelled 0 and I-VIII, some split into sub-columns A/B) across 12 horizontal series, producing the first periodic table built on a stated law (Table 3.4). …
| Series | Group 0 | Group I | Group II | Group III | Group IV | Group V | Group VI | Group VII | Group VIII |
|---|---|---|---|---|---|---|---|---|---|
| 1 | - | Hydrogen H 1.0008 | - | - | - | - | - | - | - |
| 2 | Helium He 4.0 | Lithium Li 7.03 | Beryllium Be 9.1 | Boron B 11.0 | Carbon C 12.0 | Nitrogen N 14.04 | Oxygen O 16.00 | Fluorine F 19.0 | - |
| 3 | Neon Ne 19.9 | Sodium Na 23.5 | Magnesium Mg 24.3 | Aluminium Al 27.0 | Silicon Si 28.04 | Phosphorus P 31.0 | Sulphur S 32.06 | Chlorine Cl 35.45 | - |
| 4 | Argon Ar 38 | Potassium K 39.1 | Calcium Ca 40.1 | Scandium Sc 44.1 | Titanium Ti 48.1 | Vanadium V 51.4 | Chromium Cr 52.1 | Manganese Mn 55.0 | Iron Fe 55.9 · Cobalt Co 59 · Nickel Ni 59 |
| 5 | - | Copper Cu 63.6 | Zinc Zn 65.4 | Gallium Ga 70.0 | Germanium Ge 72.3 | Arsenic As 75 | Selenium Se 79 | Bromine Br 79.95 | - |
| 6 | Krypton Kr 81.8 | Rubidium Rb 85.4 | Strontium Sr 87.6 | Yttrium Y 89.0 | Zirconium Zr 90.6 | Niobium Nb 94.0 | Molybdenum Mo 96.0 | - | Ruthenium Ru 101.7 · Rhodium Rh 103 · Palladium Pd 106.5 |
| 7 | - | Silver Ag 107.9 | Cadmium Cd 112.4 | Indium In 114.0 | Tin Sn 119.0 | Antimony Sb 120.0 | Tellurium Te 127.6 | Iodine I 126.9 | - |
| 8 | Xenon Xe 128 | Caesium Cs 132.9 | Barium Ba 137.4 | Lanthanum La 139 | Cerium Ce 140 | - | - | - | - |
| 9 | - | - | - | - | - | - | - | - | - |
| S.No. | Property | Eka-aluminium (Predicted) | Gallium (Observed) | Eka-silicon (Predicted) | Germanium (Observed) |
|---|---|---|---|---|---|
| 1 | Atomic weight | 68 | 70 | 72 | 72.59 |
| 2 | Density (g/cm3) | 5.9 | 5.94 | 5.5 | 5.36 |
| 3 | Melting point | low | 29.78 °C | High | 947 °C |