In reply to Jones Beene's message of Tue, 30 Jan 2007 15:39:11 -0800 (PST): Hi, [snip] >Well you take a metal which is denser than aluminum, and combine it with a gas >into a ceramic, and instead of the result averaging out to be less dense, it >is considerably denser, indicating the the oxygen is "located", so-to-speak - >way inside the original Barium atom and the duet has shrunken even more. This >sort of thing happens with aluminum as well, and a few other light metals - >whereas iron and the other metal (oxides) are far more typical, with the oxide >being considerably less dense than the metal.
Because Barium is a rather large atom, the valence electrons are far removed from the nucleus, and hence occupy a rather large diameter orbit (Atomic radius = 2.78 Angstrom). When combined with a small atom like oxygen which removes those valence electrons the remaining barium ion is considerably smaller (1.42 Angstrom), hence the increase in density. Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
