how does and atom move around the nucleus?

Question

in chemistry how does an arom move arund the nucleaus

Answer 1

Hi Alex,

  An atom consists of a nucleus surrounded by a 'cloud' of electrons.  The nucleus is compose of protons and neutrons in most cases (Hydrogen only has a proton in the nucleus.)  Based on this description the nucleuos is part of the atom so the atom does not move around the nucleus.

  The question might be better stated as 'In an atom, how do electrons move around the nucleus?'  

This depends on what level of quantum mechanics you are using to describe the atom.  In the Bohr Model, created in the early 20th century, the electrons moved in disctinct orbits govern by electromagnetic forces between the nucluse (it has a net positve charge) and each electron (each has a negative charge).  As quantum mechanics progressed, the 'Heisenberg Uncertainty Principle' dictated that the momentum and position of a particle could not be simultaneously defined exactly (Δx * Δp ≥ h/2*Pi, where x = position, p=momentum, h= Planck's constant).  With this constraint the location and movement of an electron near the nucleus is 'uncertain'.  Thus physicists and chemists talk about an electron as being distributed around the nucleus...in a  'cloud'.  (No, not the cloud connected to your phone!  ;-)  )

   These two descriptions of the electron's behavior highlight two competing ideas in physcis:  Is the universe deterministic (like the Bohr model) or does the universe behave in a probabalistic manner (as decscribed by Heisenberg's uncertainity principle).

  Food for thought!

BruceS

Answer 2

Should point out that both nucleus as a whole and electrons could be thought of as mutually circling their common center of mass -- but because electrons are so-o-o-o much lighter than nucleons, that center of mass is essentially at the nucleus. That portion of behavior is a consequence of rest-masses of the respective particles involved. Then, on top of that, is the quantum behavior of the lighter electron (with orbital shapes, and all that).

By experimental artifice other charged particles can be substituted for protons and electrons in atoms (for a very short while!) and then the structure changes accordingly. Imagine, if you will, a very massive negative particle paired with a lighter positive one ("antimatter hydrogen atom") -- the positive one is now going to be doing the exterior circling, where of course it will presently run into a regular-matter electron, annihilating with emission of 511 KeV gamma rays, followed by a proton-antiproton event of considerably greater complexity and energy emission.

Re/ Heisenberg; as the joke runs, Heisenberg can't find his car keys, b/c he knows too much about their momentum ....

Answer 3

Yes the question might need to be rephrased.  You have to be familiar with Rutherford's and Bohr's model.

Rutherford discovered, based on the gold foil experiment, that the atom consists of a dense positive nucleus with negative electrons traveling around it.  His model was known as the nuclear model or planetary model.  The electrons would be considered the planets and the nucleus the sun.  

Furthermore, Bohr was even more specific about electron travel in that he revealed that they travel in orbits or energy levels.  Thus, each electron has a specific amount of energy.