We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is Atomic Theory?

Michael Anissimov
Updated May 21, 2024
Our promise to you
All The Science is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At All The Science, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Atomic theory is the idea that matter is made up of little units called atoms. When the ancient Greek philosopher Democritus came up with the idea in the 5th century BC, is was originally meant to refer to indivisible units. As of 1897, the British scientist J.J. Thomson discovered that atoms are in fact made up of smaller particles. Today, this theory refers to matter being made up of units that are indivisible only some of the time. Exceptions include plasmas, such as fire, other ionic arrangements, such as those found in the body, radioactive materials, and many more.

Even though atomic theory today is a familiar cornerstone of modern science, like germ theory or evolution, throughout most of human history, people believed that matter was probably continuous and could be broken down into arbitrarily small quantities. It wasn't until 1803, or possibly a bit before, that the English chemist John Dalton revived the old idea and used it to solve various problems that chemists were grappling with at the time. Rather than any one experiment leading to the idea, it emerged from analysis of multiple experiments involving the properties of gases and chemical reactions. His theory was popularized and confirmed experimentally over the course of the early 19th century.

Dalton's atomic theory had five main points:

  1. All matter consists of minuscule particles called atoms.
  2. All atoms of a given element are identical to each other.
  3. All atoms of a given element are different than those of other elements.
  4. Atoms of one element combine with other elements to create compounds. They always combine in equal amounts.
  5. Atoms cannot be created, divided, nor destroyed.

Most of the above is still accepted by scientists today, except for a few points. First, the discovery of nuclear fusion/fission and radioactivity prompted revision of point #2. Isotopes prove that atoms of the same element can actually have small differences due to a different number of neutrons. Also, the existence of ions with varying numbers of electrons also contradicts this point.

The fifth point is also invalidated by nuclear physics, since atoms can indeed by destroyed in nuclear chain reactions. The second item of point #4 is also quite incorrect, as, for instance, water is H2O, not HO. His insistence that atoms combine in equal amounts to create compounds held back acceptance of his theory for years. Regardless, from the viewpoint of today, Dalton contributed remarkably for his time, and his name continues to be revered by its association with the theory.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By anon1000717 — On Nov 30, 2018

I thought that a nucleus is an atom.

By Fa5t3r — On Feb 16, 2013

@pastanaga - The idea that atoms are the smallest building blocks in creation is definitely not taken for granted, and in fact, they have discovered many other particle types which are smaller than atoms (although I don't think they make up atoms, they just exist alongside them).

I don't really understand physics when it gets that theoretical though, it seems to get very complicated and slightly wishy-washy but I'm sure it makes sense to those who are studying it.

By pastanaga — On Feb 16, 2013

I think it's interesting to speculate that we may still have not found the lower limit of size for matter. Atoms might be made up of even smaller particles, there's no reason why they can't be.

I guess I kind of like the idea that size differences can go on forever, getting smaller and smaller or bigger and bigger so that space is infinite in more directions than we might think.

By KoiwiGal — On Feb 15, 2013

@anon112649 - Unfortunately a lot of the time science history tends to be a bit Western-centric, probably because when it is in English it's being written by a Westerner who might not know about other theories.

In this case though, I think it's talking about a specific kind of modern atomic theory, which is attributed to a particular person. If they were talking about the history of atoms in science, they'd have to mention a lot of other people, since the idea of tiny particles has been around for a while in both the East and the West.

By anon319327 — On Feb 12, 2013

What about Bohr? What part did he have in it?

By anon312838 — On Jan 09, 2013

Were there any problems with this theory?

By anon244370 — On Feb 01, 2012

Name five areas where the atomic theory is used.

By anon158126 — On Mar 06, 2011

What about the second point, though?

"2) All atoms of a given element have are identical to each other."

Aren't isotopes the same given element but different amount of nuclei? More neutrons?

By anon149821 — On Feb 05, 2011

What a delightfully succinct post.

By anon142322 — On Jan 12, 2011

this was short and to the point, also very understanding, thank you it was a big help and makes studying easier because of the information given.

By anon141508 — On Jan 10, 2011

Thanks! perfect for my project!

By anon138864 — On Jan 02, 2011

good site

By anon121901 — On Oct 25, 2010

thank you so much for this site. it got down right to the point, and had exactly everything i needed.

By anon113757 — On Sep 25, 2010

this site was to the point and precise. wisegeek

is the best!

By anon112649 — On Sep 21, 2010

This site is very helpful for my project but i felt very sorry to say that our indian philosopher rushi kanaad's reference is not in this page. - vibha s.

By anon104419 — On Aug 16, 2010

thank you so much! This was very helpful, and i also decided who to do my project on. I had to figure out what atomic theory was before i could do the project on it.

By anon97548 — On Jul 20, 2010

thanks for helping me to understand the atomic theory. now i know!

By anon94872 — On Jul 10, 2010

thank you very much.

By anon70783 — On Mar 16, 2010

thanks very much for this website. It has helped me and my partner to complete our task! thanks again.

By anon68614 — On Mar 03, 2010

this website helped me a lot in science class!

By anon67948 — On Feb 27, 2010


By anon67292 — On Feb 24, 2010

Thanks. you helped a lot.

By anon65883 — On Feb 16, 2010

This site was great! it helped me actually understand atomic theory and helped a lot on my project. thanks!

By anon65735 — On Feb 15, 2010

this site was all i needed for my project. thanks!

By anon44088 — On Sep 04, 2009

This site was very helpful for my project. thank you to the wisegeek creator!

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology...
Learn more
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.