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Q & A: atom shape

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Most recent answer: 06/03/2009
Q:
What is the shape of an atom.Is it spherical or oval,elliptical.etc..
- Prudhvi Raj.Borra` (age 16)
Machilipatnam,Andhra PRadesh,India.
A:
Some atoms are perfectly spherical. Even though an atom doesn't have a distinct edge, since the electron density gradually falls off, wherever property you choose to measure on these atoms is the same no matter what direction you look at the atom from. Hydrogen, helium, lithium, and neon are examples of such atoms.  (In some cases the combination of spin-orbit effects and interaction with nuclear spins and lead to very tiny deviations from perfect sphericity.)

Most atoms, however, have some angular dependence of their properties. You can find pictures of the shapes of some of the atomic orbital states and a nice discussion on wikipedia. Atoms which have some electrons with these highly non-spherical states, but not the right number to fill up a 'shell' and thus become overall spherical again, end up with strongly non-spherical electron densities, etc. The resulting shapes of the contours of electron density are not ellipsoids.

Mike W.

(published on 06/03/2009)

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