Topic 5 – Atoms and Isotopes

Isotopes of lithium

Image from “Russell’s Blog” which you can access by clicking on the image

Last time we talked about the important parts of atoms – protons and electrons – and how they come together to define the unique properties of every element.  Now let’s tackle the one remaining part, which is how neutrons fit into the mix.  Remember, neutrons and protons are practically the same thing in terms of mass, except the proton carries a positive charge.  The neutron even says it in the name.  It is neutral, meaning no charge, just mass.

That mass is what the neutron brings to an atom.  The mass of an atom is dictated by the number of protons and neutrons.  The identity of an atom is defined by the number of protons, so a given element will always have the same number of protons.  Lithium always has three protons, carbon has six protons, iron has 26 and so on.  The number of protons is so important, it is called the atomic number and you will find it on every periodic table you will see.   Continue reading


Topic 2 – Dalton’s Atomic Theory

The Evolution of the Atom

This shows the evolution of the model of the atom. It begins at top left with Dalton’s idea of an indivisible particle and moves to the left until Bohr’s model appears in the lower left. Bottom right is a modern representation.

Last time, I introduced the atomic nature of the physical universe. This time we will look a little deeper at its roots.

The history of chemistry goes back thousands of years, probably starting with the alchemists, and it’s interesting. The alchemists might be among the greatest con men of all time. That period in the development of science is a great story for another time.

When thinking about atoms, we start much later in history, with the work of John Dalton who contributed the major portion of his work around 1800. His model of the structure of matter marks the beginning of modern chemistry and while today, we know he missed the mark on a couple of his assertions, his basic model still serves as a simple way to understand much of the physical universe. Continue reading

What This is About

Hello.  My name is Rick Fletcher.  I’m a human and as a big part of my work, I’m a professor of chemistry at a medium-sized research university in the USA.  I also think about physics a lot and more and more, I am interested in the ways these two areas collide with other areas of science and life in general.  The tools used in chemistry and physics are powerful ways to understand the physical world around us.

For several years now, I have been teaching my college’s most basic chemistry class.  If you’ve been to university, you probably had a version of this, or know what it’s like.  These are usually among the largest classes offered in higher education.  I try to be a good “explainer” of as much as I can.  Even though I prefer to have my time in this class rotated in and out, I keep getting the assignment again and again.  I’m told that happens because I get very few complaints.  I hope that means I do a fairly good job of “explaining.”

So, that’s what I will do here.  At least once a week, and hopefully more often, I’ll pick a small topic in science and explain it to a general audience.  Part of being a good explainer is to be brief and to not waste anyone’s time.  These will be my two guiding principles.  I’ll try to limit to One Thing, but as you will see, that means that I will focus on one concept but I might use several supporting ideas to explain that one thing.  I will try to do things in a progression so I can refer back to earlier posts if I need to rely on more than one idea in any given post.  But please remember, the theme here is simplicity.  To keep things brief and simple, I might not always be as detailed as the reader hopes but that’s not my goal.  I want to show the world that the physical world can be understood by more than scientists.

I was inspired to do this by Alan Alda’s Burning Question, sponsored in part by The World Science Festival, which is an interesting organization.  Alda asks scientists and engineers to explain a flame to an audience of 11-year-old students.  I think we need more of that, and I hope to help in some small way.  So at least once a week, I’ll try my best to Explain One Thing.