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A if ago, I composed a couple of posts describing part intra-molecular forces, pressures that hold atoms and molecules together. I enjoyed writing them, and people come back to review them quite frequently, for this reason I thought I"d continue and write about a couple more.

You are watching: What holds an ionic compound together

The previous write-ups covered valve der Waals forces and also hydrogen bonds (and dipoles!) These forces are both fun, and also incredibly important in identify the nature of water (without i beg your pardon there would be no life) and petrol (without i m sorry there would be no cars) but they aren"t particularly strong forces. Both van der Waals and also hydrogen bond are reasonably weak, and I think it"s about time ns started spanning the three big Bads of molecular forces: ionic bonds, covalent bonds and metallic bonds.

Starting through ionic bonds. In order to correctly cover these, i need simply a small bit of elevator on what atoms space actually like. Now there are plenty of different models because that what atoms space "like" yet for the purposes of ionic bonds the easiest method to think of castle is as a tiny nucleus through a positive charge surrounded by little whizzing negatively fee electrons. Electrons don"t simply all fly around with no direction, castle exist in orbitals, every a various distance native the nucleus. To uncover out how many electrons room in the outermost orbital, furthest away from the nucleus, you have the right to look at the regular table.

The outermost orbit is the most important because all the various other electrons room a) in orbitals v the maximum variety of electrons and also b) unable to take it much component in reactions as result of the outermost electrons being in the way. Atoms in general are in ~ their many stable as soon as they have actually a full outer covering of electrons. As numerous atoms don"t have a complete outer covering of electrons, they shot to discover ways of gaining one.

Take sodium, because that example, through the chemistry symbol Na (blame the Greeks for that!) now sodium is in the first column of the routine table, therefore it has one electron in the outermost shell. Every the other shells are full of electrons. So the quickest way to gain a complete outer covering is to loosened that outermost electron, leave you with a complete shell underneath. Loosing one electron, however, needs energy, which way that unless this have the right to be linked with a process which produces energy, that is not going come happen.

Loosing one electron also way that rather than having an equal variety of positive atom charges and an unfavorable electron charges. The salt now has actually one fewer negative charges. Rather of a neutral sodium atom, that is currently a positive charged salt ion.

So how does the sodium acquire the power back? One means of producing a lot of energy in the civilization of molecular forces is to kind a bond. Break bonds needs energy, yet making them produces power (ask a physicist around this if you"re unsure why, the explanation can not do you any an ext sure yet it"s nice for physicists to have someone to speak to). Luckily, a positively fee ion is very an excellent at developing bonds through a negatively charged ion.

To see just how a an unfavorable ion forms, take a look at the various other side of the regular table in ~ the element chlorine. Chlorine has seven electrons in its external shell (a full shell is eight electrons because that the smaller elements). In stimulate to to fill its external shell it deserve to take one electron acquiring one extra negative charge and also forming the negative chloride ion. The doesn"t simply take the electron from anywhere, it will actually tear it far from the sodium atom. Leaving one negative and one confident ion; Na+ and also Cl-

The shortcut formed in between these ions is dubbed an ionic bond.

The 2 ions don"t just kind a single bond in between them, ideally they want to make as countless bonds as possible. Ionic bonds develop giant ionic lattices the interchanging ions. These are extremely strong, do ionic compounds an extremely hard come break, melt, or crush.

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Not just do ionic forces help to hold facets together, the formation of this bonds can totally change the properties of the facets they bind. Salt is a soft grey metal (you can reduced it v a knife!). Chlorine is a deadly green gas. The giant ionic lattice salt chloride is salt, a white grainy edible food.


Credit for picture 2

Credit for photos of chlorine, sodium and magnified salt crystals provided in photo 3

The see expressed space those that the author(s) and also are not necessarily those of scientific American.



A biochemist through a love the microbiology, the LabRat enjoys exploring, reading around and writing about bacteria. Having finally controlled to tear herself far from university, she now works for a little company in Cambridge where she turns data into controlled words and awesome graphs.Follow S.E. Gould top top Twitter