In the last few posts, the atomic nature of the universe was discussed, Dalton’s atomic theory explained and we took a tour of the “guts” of an atom. Now let’s use all this to understand how the pieces fit together to illustrate what makes the element (and atom) hydrogen, different from carbon, oxygen and neodymium. The short story is the way the parts come together – it’s really a counting game.
A new element is discovered almost every year – but for now, a current periodic table will show 118 unique elements. (I’ve linked this image to a good table you can print out if you wish.) All periodic tables will have at least 3 pieces of information. For each element, every table should give you at least the symbol, the atomic mass and the atomic number. Some have far too much information, stuff you should be able to infer from the position on the table, they symbol, the mass, and so on, but every table – except the ones on the shoes at the top of this post – should give the three fundamental data. Of these three, the most important is the atomic number. So important is the atomic number, notice it provides the organizing principle for the arrangement of the atoms. Continue reading