3) when zircon (zrsio.) crystallizes from a magma, it commonly admits u4 into its crystal structure, but strongly excludes pb. deduce the valence of pb in magma from this observation. show your reasoning. the two main types of meteorites found on earth are the iron and the stony what exactly are meteorites, where do they come from, and what do these two types tell us about the composition of the earth? 4) 5) in each of the following pairs, choose the one in which the chemical bond would have more covalent character a) kcl and ki b) li, s and cs, s c) bacl, and hgcl d) kcl and bac e cu, o and cu2s