So water molecules are like a boomerang with a negative bend in the middle and two positive ends. With its two hydrogens flanking one oxygen atom, the electron cloud around water has a fat bulge around the middle, and fairly sparse coverage of the hydrogen nuclei around the ends (see diagram). Molecules with patchy electron clouds like this are called polar, and water (H 2O) is the king of this bunch. That patchy covering means some parts of the molecule are more negatively charged than others. The electron cloud coverage over these molecules is patchy - it's more dense around atoms that are good at attracting electrons (oxygen is notorious for this) and less dense around weak electron attractors like hydrogen. If the atoms are well matched in terms of their electron pulling power, you end up with an electron cloud that's the same density around the whole molecule.īut a lot of molecules are made of atoms that are not evenly matched in electron pulling ability. Chemical bonds between atoms in a molecule are just overlapping electron clouds, with the different positive nuclei vying for their share of the negative electron clouds. ^ to top Electron clouds and stormy weatherĪll atoms have a positive centre (the nucleus, where the protons are) and a negative electron cloud around them. But that chink is enough to let water molecules reach the chemical bonds inside - and that's where things like skin and metals go all to pieces. (Source: Mr_Kermit/iStockPhoto)Īcids come with warning labels for good reason - any acid much stronger than vinegar can cause a nasty burn to your flesh, or a fizzing pit in your metal surfaces.īut when you get down to the chemistry of what's going on, it's clear that acids are getting a bad rap.Īcids don't tear things apart on their own - all they do is put a chink in the electron armour surrounding molecules. Bubble-07: acid gives water a licence to kill.
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