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What is found on the outside of a nucleus?
Question Date: 2015-02-19
Answer 1:

An interesting question! It really makes you think about what matter is actually made of.

The approximate size of an atom is about 10-10 m (this is for fairly large atoms). Here, I use something called scientific notation where powers of 10 are represented with exponents, so 10-10 m= 0.0000000001 m = 1/10,000,000,000 m. That's tiny! But the nucleus is even smaller at only around 10-15 m; it is five orders of magnitude smaller than the atom itself at around 0.000000000000001 m. (There are so many zeros, I had to count thrice!)

How to imagine a number this small?
Take a look at the tip of one of your hair strands. On average, people's hair is around 100 microns (i.e., 10-6 m). You could fit about one million atoms just across the diameter of your hair!

What about the size of nucleus relative to the atom?
Imagine that you were the nucleus. A person is about 1 m across. The boundary of where the edge would be is about 105 m = 100,000 m away. That's almost 2.5 marathons (or 65 miles)! I don't think you could see that far.

So the nucleus only takes up a small fraction of the volume of an atom. Does this mean the atom is mostly empty space? Sort of.

The nucleus is surrounded by electrons sloshing around, but these electrons are not particles that whizz about. Once you get to atomic length scales, quantum mechanics starts to kick in and you need to start describing things as having wave-like character.

The key notion is there is a certain probability of finding the electrons somewhere, and some places are more likely than others. You can see the beautiful complexity that electrons fill atomic orbitals and slosh about around the nucleus here

What really causes interesting properties to arise is really the interaction of all these electrons and nuclei when put in different configurations and crystal structures! And this is known as the study of materials science.

Hope this helps,

Answer 2:

In science, the word "nucleus" has several different meanings. I am going to assume that you mean the nucleus of an atom.

The nucleus of an atom contains the protons and neutrons in the atom. Surrounding the nucleus is a cloud of electrons, much larger than the nucleus but containing only a tiny fraction of the atom's mass.

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