What is the relevance of the arrangement of electrons around the nucleus?
Valency (at GCSE only level mind I'm no pro) is the charge on an ion of an atomSo Chlorine goes to the Chloride ion in a reaction, which has a valency of Cl1-Some atoms have variable valency (a.k.amore than one possible ion for the same atom) such as iron, which can go to either Fe2+ or Fe3+By the way, ions are formed when an atom gains or loses one or more electrons, which are negativeSo Fe goes to Fe2+ by losing 2 electronsThe reason some atoms lose electrons and other's gain electrons is to do with the shellsElectrons are arranged in shells around the nucleusThe first shell can have a maximum of 2 electrons, the second a maximum of 8, and the third a maximum of 8I'm not sure about what happens after the 3rd shell, bu those are the basicsIf an atom has 2 electrons they will both be in the first shell, and if it has three, then 2 will be in the first shell and 1 will be in the 3rd shellIn the periodic table, the atomic number of an element (the smaller one at the bottom) is the number of protons, and therefore also the number of electronsBy this number you can work out the arrangement of the electronsSo Aluminium, 13, must have 2 electrons in the first shell, 8 in the second shell, and the final 3 in the third shellAn atom that has exactly 2 (2), 10 (2,8) or 18 (2,8,8) (and so on) electrons, i.ethe maximum number for each shellWhen atoms lose or gain electrons, they try to achieve this stateSo Lithium, with 3 electrons, arranged therefore as (2,1), loses 1 electron when it ionises to become Li+, arranged (2), whereas Chlorine, 17 (2,8,7) gains an electron to become Cl-, arranged (2,8,8) a more stable stateThis is how to determine the valency of the ion(s) of an atom, although until you get to more advanced level Chemistry, you simply learn a long list of what ions the atoms go tohope that helped, otherwise look it up in a textbook.
if its cheap, its cheap for a reasonplastic + heat
