For example, fluorine could be written as 1s 22s 22p 5, and neon as 1s 22s 22p 6. Shortcut 1: All the various p electrons can be lumped together. There are two ways around this, and you must be familiar with both. You can see that it is going to get progressively tedious to write the full electronic structures of atoms as the number of electrons increases. The next electrons to go in will have to pair up with those already there. You wouldn't normally write them any differently from the other orbitals. Note: The orbitals where something new is happening are shown in bold type. These levels all have the same energy, and so the electrons go in singly at first. Beryllium adds a second electron to this same level - 1s 2 2s 2. Lithium has an electronic structure of 1s 2 2s 1. Lithium's electron goes into the 2s orbital because that has a lower energy than the 2p orbitals. Now we need to start filling the second level, and hence start the second period. Hydrogen has its only electron in the 1s orbital - 1s 1, and at helium the first level is completely full - 1s 2. If you are studying a UK-based syllabus and haven't got them, follow this link to find out how to get hold of them. Important! You must have a copy of your syllabus and copies of recent exam papers. This page looks in detail at the elements in the shortened version of the Periodic Table above, and then shows how you could work out the structures of some bigger atoms. It is important that you look through past exam papers as well as your syllabus so that you can judge how hard the questions are likely to get. After barium you have to worry about f orbitals as well as s, p and d orbitals - and that's a problem for chemistry at a higher level. UK syllabuses for 16 - 18 year olds tend to stop at krypton when it comes to writing electronic structures, but it is possible that you could be asked for structures for elements up as far as barium. This isn't a mistake, but an effect of converting my original diagram into a lower quality gif image for efficient web use. Note: On some screens the V for vanadium (element 23) may look a bit like a Y. Relating orbital filling to the Periodic Table Important! If you haven't already read the page on atomic orbitals you should follow this link before you go any further. If you want to look at the electronic structures of simple monatomic ions (such as Cl -, Ca 2+ and Cr 3+), you will find a link at the bottom of the page. It assumes that you know about simple atomic orbitals - at least as far as the way they are named, and their relative energies. This page explores how you write electronic structures for atoms using s, p, and d notation.
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