an electron revolves around a nucleus why cant it be stationary?

Answer 1

In a sense it can be. Keep in mind, though, you're thinking classically, and this will fundamentally limit your understanding of such things. An electron is actually represented by a continuous function distributed about the nucleus called a wave function. However, just as in the classical description, it does have orbital angular momentum, which is zero when the orbit has as low of energy as possible (ground state). The wave function in that case is spherically symmetric. It cannot fall into the nucleus, as it would classically, because that's the minimum energy solution to the wave equation it must obey.

Answer 2

You got some good answers above already, I'm voting for descendan's answer to be the easiest for visualization, but I like Dr. R's answer the best. However, I'm guessing you might not know what is a "wave function", or what is the "Uncertainty Principle", or what does "act like particles or act like waves" mean, otherwise you wouldn't be asking this question.

Here's another way to look at it, basically, if the electron is stationary (no kinetic energy), then it cannot be in "orbit" around a nucleus. Lets not go into what would happen if the election is to be initially stationary near a nucleus, that's a different question.

It's like if you hold out a rock at arms length and let it go, it'll initially be stationary, but soon it'll fall back to the ground. Without some kinetic energy to keep that rock in orbit, it'll fall (Newton draw a nice picture to explain about satellites). See this:
http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/DiscoveringGravity_files/image004.jpg

So, for an electron to "revolve" around a nucleus, it must have a certain amount of kinetic energy, to be in a stable "orbit".

Answer 3

How can it possibly be? The electron is subjected to the attraction of the positively charged nucleus, how could it remain stationary in space? What would keep it hovering above the nucleus?

Answer 4

SHEESH, are they trying to confuse you or what?!
The model of an electron as a particle is only that! A model.
Electrons are not proven to exist as particles. They "act" like particles of matter at sometimes and "act" like waves at other times.
When you are first taught about atoms, you are told things like they were facts. NONE of these are TRUE facts. They are theories that help explain the behavior of atoms. The atom is not just a little "solar system".
The most helpful interpretation of electrons is that of a cloud of "probability" that the electron could be at any one point in the cloud. When you look at it that way, you can understand better that the electron is not a orbiting tiny ball of matter but a different entity with properties that we don't fully see with any one model.

Answer 5

The same reason the moon has to revolve around the earth. If it stopped, gravity would cause it to crash into us.

An electron that didn't revolve around the nucleus of the atom would be drawn into it by the positive charge of the proton.

Answer 6

While the above answer is not incorrect, particles cannot be stationary, because then there would be no uncertainty in their momentum. Momentum is mass times velocity, so zero velocity would mean zero momentum.

The Uncertainty Principle states that we cannot know certain quantities exactly, and that if we gain information about one (such as position) we must sacrifice information about another (such as momentum).

Velocity is therefore not something that we ever know exactly, and neither is position.

Answer 7

You can slow it down with absolute 0 degree temperatures. also if it bonds to another electron, it becomes the matrix of a crystalline solid.

Answer 8

This site may help.

http://einstein.byu.edu/~masong/HTMstuff/textbookpdf/C17.pdf