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We are currently studying atoms and the periodic table. A student asked a question today that I thought was quite perplexing. Since an atom is mostly empty space between its nucleus and electrons, what exactly is that "empty space?" From my amateur point of view it can't be a vacuum, can it? And, there can't be matter of any sort because we're on such a small scale (and atoms make up matter). Thanks for the help. Love the site. Confused by the empty, PJ Creek 8th grade science teacher.
Question Date: 2017-11-29
Answer 1:

Excellent question, which is actually a bit of a complicated question to think about.

Quantum mechanically (I know, I know) you should consider a few things:
These sub-atomic particles like electrons, protons and neutrons are quantum objects. They have what is known as a wavefunction which can be considered a likely area, or probability, of the particle's location.

Electrons are quite spread out around the nucleus, which is why this area is referred to as an electron "cloud". So, electrons are smeared over all of this "empty" space. Additionally, the particles of the nucleus and the electrons of an atom are constantly interacting, either electromagnetically or through what is known as the weak force. These particles are exchanging photons (in the case of electromagnetism) or heavy gauge bosons (in the case of the weak force ). So you can say that the 'empty' space between the electrons and nucleus is 'filled' by these forces.

I think it is fine to call what is in between everything empty space in the atom if you took a snapshot of the atom, but also consider that there are also energy fields and the probability of an electron occupying that space all at once in reality.

Hope that helps!

Answer 2:

In fact, there is no "empty space" in an atom.

To understand this, we need the full quantum mechanics understanding of electrons. In quantum mechanics, an electron is not a point particle, it is a distribution of "probability cloud" (wave function of the electron), usually called the "electron cloud".

So in an atom, the nucleus is surrounded by electron cloud in the full space inside an atom, so there is actually no empty space between nucleus and electrons.

According to quantum mechanics, nucleus itself is also a "cloud", but because nucleus is much heavier than electron, the size of its cloud is very small, so usually we can still view nucleus as a point.

Answer 3:

In the classical picture, the electrons will orbit around the nucleus in the fixed orbitals , pretty much like the planets orbiting around our sun with lots of empty space in between. But there is one big development in the 20th century, which is the idea of quantum effect. When things are getting so small, quantum effects are not negligible anymore and will play big roles.

In the modern picture, the electrons will still orbiting around the nucleus, but with no fixed orbitals (here I mean those classical orbitals). Instead, those electrons are constantly moving, with probabilities to show up around the nucleus. We still use the orbitals to describe the motions, but the meanings are different. Here is a website that you can get a glimpse of those orbitals (s, p, d, f orbitals, etc..): orbitals

I will give one example. In the simplest case, like H atom (hydrogen). The sole electron will take the s orbitals, which is isotropic . It means that the sole electron will show up in any direction with equal probability. There is one more thing, which usually is not easily to show, the probability for the electron to show up is distance dependent (here distance means how far away the electron is to the nucleus, denoted as r ). It is a peak function, which means that the electron will show up with a maximum probability at distance r0. The important thing to know is the electron can also show up very close or very far away from the nucleus, though with smaller probabilities.

In the classical picture, the electron will pretty much stay at the same distance r0 to the nucleus. But in the modern picture, it is more or less true. It has the biggest probability to stay at such distance, but it can also be closer or further away with smaller probabilities.

So those space is not the vacuum that we are usually talking about.

Answer 4:

Good question!

What is actually happening is that each particle inside of an atom has a cloud of probability as to its actual location , with the electrons having large (r) clouds while the protons and neutrons have tiny clouds in the very center. These clouds of probability take up the entire size of the atom, and they overlap - for example, the probability clouds of the two electrons in a helium atom perfectly overlap one-another.

Indeed, electron "orbitals" (cloud sizes and shapes) come in pairs, which is why the length of every period in the table is a multiple of two (H to He is 2, Li to Ne is 8, Na to Ar is 8, K to Kr is 18, and so on). So, technically, the space in an atom is not vacuum, because it is filled with these probability clouds.

In order to fully understand what is going on, you need a little understanding of Mquantum mechanics, which explains why different elements fall where they do on the periodic chart. Working this out is the discovery for which Richard Feynman won the Nobel Prize (the theory of quantum electrodynamics as it is called). A good, college freshman-level chemistry textbook should explain it in detail well enough for you, an adult, to grasp it.

Explaining it to eighth graders then becomes trickier as it involves mathematics that is just at or slightly beyond their level. For example, the length of any period is given by the following formula:

L = 2 x (((n + 1) / 2)2)

where n is the number of periods down in the table (round fractions up to the nearest integer). So, 2, 8, 8, 18, 18, 32, 32, 50 - and that's all of the elements that we've discovered that are stable because of nuclear physics, but if there were more stable elements, in a neutron star perhaps, then the sequence would just continue.

Answer 5:

This is a great question! You’re right it saying that the space between the electrons and the nucleus is empty space but it’s important to keep in mind the way that electrons move. They don’t orbit the nucleus at a set distance rather they exist at multiple locations in a sort of cloud around the nucleus. The electrons are moving so quickly through such a small space that it almost seems like they are in multiple spaces at the same time! In fact the quantum field fluctuations that the electrons cause almost fill up this entire space around the atom. This video may be a little advanced for your class but the visual demonstrates the idea very well:

watch here .

Thank you for your question!

Answer 6:

The simple version of the story is yes, it is empty space even though it is weird to think about.

Nearly all the matter that makes up an atom is in the nucleus, but the size of the atom is determined by the radius of the outer electron shell, so most of the atom is indeed empty (i.e. is not made up of matter). The reason that I cannot (unfortunately) walk through walls is because the electrons that make up the outer shell of my atoms repel the outer electrons in the atoms that make up the wall. However, there are particles that do not interact with the electromagnetic field, and these can pass through atoms. For example, neutrinos are small particles, which do not feel the electromagnetic force and thus can fly right through walls (or the earth itself), because the wall is mostly empty space.

neutrinos .

A more quantum mechanical perspective would say that the simple picture of a point electron sitting in a defined location around the nucleus is not really correct. It is more realistic to conceptualize the size of the atom as being defined by an electron cloud of probability. There is a finite probability to find an electron anywhere inside the cloud region and so the space around the nucleus is really occupied by some electron probability density or field. Think about a magnetic fieldas an analogy. The magnetic field occupies a volume, but it appears that there is nothing there (empty space), and I would not know it was there unless I put a magnet into the field and observe that the magnet is pushed by the field.

Try pushing two north sides of a magnet together and you will see they repel each other. On the atomistic scale this is very similar to what is going on when I put my hand against the wall.

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