Posted 21 April 2007 - 05:16 PM
I'm assuming you know the basic trend in electron configuration is 1s1, 1s2, 2s1, 2s2, 2p1, etc... The first configuration represents the hydrogen atom, as it has 1 electron in its first electron shell. The second would be helium, as it has 2 electrons in its first shell. The next one is lithium, which has a configuration of 1s2 2s1, because it has 2 electrons in it's inner shell(n=1) and one in its outer shell(n=2). When we're dealing with ions, all we have to do is look at how many electrons were lost or gained by the atom, and subtract or add electrons accordingly, and match the electron configuration that coresponds to it. The ion may have the same electron configuration as another atom. When this happens we say that the atom and the ion are isoelectronic, that is, they have the same number of electrons. In predicting ionization, you want to keep in mind that an atom is most stable when it has 8 valence electrons. Thus Lithium wants to lose an electron to gain its octet, and fluorine want to gain an electron to achieve its octet. This idea allows us to predict charge. As for transition metals such as Zinc, its a bit trickier to predict which electrons will leave which shells. Hopefully someone else here can explain that.