---------------+------------------+--------------+----------------+ | |Hydrogen 1·01|Helium 4·2| | | | | Nitrogen 14·0|Oxygen 16·0|Fluorine 19·0|? | | | | | Phosphorus 31·0|Sulphur 32·1|Chlorine 35·5|Argon 39·9| | | | | | | |{Iron 56·0| Vanadium 51·4|Chromium 52·3|Manganese 55·0|{Cobalt 58·7| | | |{Nickel 58·6| | | | | | | |{Ruthenium 101·6| Niobium 94·0|Molybdenum 95·7|? 100·0|{Rhodium 103·0| | | |{Palladium 106·3| | | | | Neodymium 140·8|Praseodymium 143·6|Samarium 150·0|? 152, 153, 154 | | | | | | | |{Osmium 191·3| Tantalum 182·5|Tungsten 184·0|? 190·0|{Iridium 193·0| | | |{Platinum 194·3| | | | | ? |Uranium 240·0|? 244·0| | ---------------+------------------+--------------+----------------+ The elements in the first column all agree in that they are white soft substances, with metallic lustre, but tarnish rapidly in air, owing to the action of water-vapour; they are all violently attacked by water, and they are without exception monads, that is, they replace hydrogen in its compounds atom for atom. The elements in column two are also all white metals, attacked by water with more or less ease; but in their case one atom replaces two atoms of hydrogen, whence they are called dyads, or bivalent elements (worth two). And so on with the other columns. All elements in vertical columns exhibit chemical similarity, and, indeed, are often strikingly like in properties.