Since we do not have a microscope powerful enough to actually look at the atoms in a molecule, how do we know the exact molecular structure like bond length, bond angle etc. of a simple compound?
In: 2
>Since we do not have a microscope powerful enough to actually look at the atoms in a molecule
[Excuse you..](https://www.youtube.com/watch?v=pGWSX6pStd0)
The key is in the word *look*. At subatomic scales, we’re not talking about magnifying light anymore. We use electron microscopes which fire a beam of electrons at the object.
Yet your question still stands: how did we know those things before the invention of the electron microscope? Well, it’s a whole subject we call valence shell electron pair repulsion theory. In essence, the way the particle behaves and what atoms comprise it can be used to infer details about its geometry. The simplest one is water: we know the angle between the two hydrogen atoms is bigger than 90° because the lone pair electron repulsions are greater than the bond pair ones.
there are a whole slew of techniques used to find the structure of various molecules, most of which are found empirically. Spectroscopy methods like nuclear magnetic resonance ([NMR](https://www.youtube.com/watch?v=TTp5LeFto6s)), UV, IR, microwave or [mass spectrometry](https://en.wikipedia.org/wiki/Mass_spectrometry), etc. can be used either alone or in conjunction with chromatography (which separates mixtures into its components) to provide analysis of different aspects of the compound in question and determine its chemical makeup and structure by comparing it to known quantities. For example, since we already have the equipment, you can look at some pure hydrogen, some pure oxygen, etc., and see what it gives you. Then you look at an unknown, see the same spike hydrogen gave, and the oxygen spike, and notice the hydrogen spike is twice as big, and you can guess its H2O (big oversimplification but the gist is right).
There are also imaging methods like neutron or [x-ray diffraction](https://en.wikipedia.org/wiki/X-ray_crystallography#X-ray_diffraction) that can be used to determine arrangement of atoms in a crystalline structure, which also will give bond lengths and angles. So if it is something you can make into a crystal through reactions, you make it, then throw x-rays through it to “see’ what it looks like
Latest Answers