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Gold/Mining/Energy : Gold and Silver Juniors, Mid-tiers and Producers -- Ignore unavailable to you. Want to Upgrade?

To: E. Charters who wrote (43504)	6/29/2007 1:02:10 PM
From: AuBug	Read Replies (2) \| Respond to of 78424

Chemists Strike Gold With New Gold Catalysts Science Daily — Few people look beyond gold's glitter and rarity, but chemists have found that its chemical properties are just as interesting, making it a unique catalyst for producing unusual organic molecules. UC Berkeley's Dean Toste, a leader in the area of gold catalysis, attributes these properties to relativistic effects in the gold atom, the same effects that give gold its yellow luster. Essentially, gold catalysts are 'hot' because their electrons are heavy, this chemist proposes. ... One of the key tenets of relativity is that nothing can travel faster than the speed of light. The reason for this is that objects become heavier, or more massive, the faster they go, with the mass approaching infinity as the object approaches the speed of light. In an atom, where electrons race around the nucleus like buzzing bees, the velocity of an electron doesn't get anywhere near the speed of light until the atomic nucleus fills up with lots of positively charged protons - the negatively charged electrons have to move faster to keep from being pulled into the highly positive nucleus. This occurs in the transition metals of the periodic table of elements, metals ranging from tantalum and tungsten to platinum and gold. In a gold atom, with 79 protons in the nucleus, the 79 electrons whip around the nucleus at about half the speed of light. The net effect is that gold's electrons are much heavier and are pulled in closer to the nucleus, lowering the energy levels and making the atom more compact. According to this hypothesis, gold's s shells, which are its lowest energy spherically symmetric electron shells, contract. This shields the electrons in outer, asymmetric p and d orbits from the nuclear charge, allowing them to expand slightly. In gold, the contraction of the outermost (6s) shell and the expansion of the next-inner (5p) shell reduces the energy difference between the two to the equivalent of a photon of blue light. This allows gold to absorb blue light and, thus, look yellow. Silver, because it exhibits a much less dramatic relativistic effect, is unable to absorb any visible light and is totally reflective. Toste proposes that this same shielding effect allows the more tightly bound s shell to easily accept electrons from other molecules, while the partly shielded d shell can easily donate electrons to a reaction. Thus, gold is able to participate in reactions both as a donor and as an acceptor of electrons, which makes it particularly useful in catalyzing reactions at carbon-carbon bonds, the backbone of all organic molecules. According to Toste, a gold atom can attach to carbon loosely, with a single bond or a double bond, allowing flexibility in reactions that can lead to novel organic molecules. ... sciencedaily.com It takes quantum mechanics and relativity to explain why gold is yellow ;-)