Answer:
1. Rutherford did the scattering experiment and observed that some of the rays bounce back. He concluded that there is a mass in which positive charge is concentrated. This marks the discovery of nucleus.
2. J.J Thomson discovered electrons by conducting cathode ray experiment.
3. Dalton postulated that matter is made up of small particles caled atoms
The shape of the molecule depends on how many electrons and bonds you have in the outer shell of the central atom.
For NH3, N is the central atom. It has 3 covalent bonds and a lone pair. Thus the repulsion of the lone pair electrons and the bond electrons will force them to arrange at the corners of a tetrahedral. The molecule will look as a trigonal pyramid (since the lone pair is not "visible" in the structure.
<span>For BH3, B is the central atom and has no lone pair apart from the three bonds. So the repulsion of the bond electrons will force them to be in a planar trigonal arrangement.
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No but i am glad i havent
Chemical reaction, generally speaking. It's a vague definition, but it's easy to remember.
