| MadSci Network: Chemistry |
Why is gold less reactive and lower conductivity than copper or silver?
For its place in the periodic table we expect gold to be more
reactive and have a lower electronegativity than silver or copper.
zinc is more reactive than cadmium, which is more reactive
than mercury; and
nickel is more reactive than palladium, which is about as
reactive as platinum.
You find the same trend in electrical conductivities: the more reactive metals are generally also better electrical conductors -- and this makes sense! Better electrical conduction implies more loosely-held valence electrons; more loosely-held electrons allows for better metallic conduction. (This trend is not always followed: silver is a slightly better electrical conductor than copper, but is somewhat less chemically reactive.)
Electrical conductivities (listed in the original as resistivities) taken from the CRC Handbook of Chemistry and Physics, 61st Edition.Whether the more reactive members of each column are near the top or the bottom depends on which end of the table you are at; fluorine is far more reactive than iodine, but rubidium is much more reactive than lithium. As the transition metals are in the middle you would expect the vertical reactivity trends to blur and shift; and in fact, while copper is more reactive than gold, I believe that hafnium is more reactive than titanium.Incidentally, gold is often used for electrical contacts not because it is the best electrical conductor but because it is perhaps the least chemically reactive of metals. Metal oxides and sulfides (the tarnish on copper and silver) are insulators and disrupt electrical connections.
For more on the properties of gold (and other heavy elements) see one of my other answers.
| Dan Berger | |
| Bluffton College | |
| http://cs.bluffton.edu/~berger |
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