1 - Energy States of Atoms
Abstract (TL;DR):
We all know about the atom and some of us even know the three subatomic particles — protons, neutrons, and electrons — that make up atoms. This article talks about the atom from the standpoint of explaining why the atom behaves how it does.
Atoms communicate through the use of its electrons, which are oriented in specific ways according to their energy state. Since atoms and their electrons naturally want to be at their lowest energy states, electrons behave in ways that get them there, creating beautiful shapes called “orbitals”.
Image via nickvdg
Updated (3/2025)
How does one explain the relationship between one element and another? Sure, you could use the word “electrostatic” or explain it by going into depth about “electronegativity”, but those aren’t immediately relatable. If I were to put an explanation into more understandable words, I would say that it’s a game of sharing - sharing that happens the same way almost every single time according to both size and state of matter. Some reactions occur naturally just by distance. Some may only occur in the present of some outside energy source like heat. Reactions between the elements, thus, play a game of give and take.
But give and take what? And why? These questions define atomic relationships and, by extension, the way our world and our universe has formed and will continue. So, for the “beginning” of our journey, let’s try to answer those questions.
A Negative Charge
There’s a currency that atoms utilize to communicate with each other - the electron. The electron is a mass that has a negative charge, which, like the two ends of a magnet, means that it is attracted to masses with positive charges and can’t stand other negatively-charged masses.
Image via ChemistryJokes
In fact, it’s a positive charge that keeps the electrons from flying away. The core of any atom - the nucleus around which electrons move - is normally composed of protons and neutrons (excluding hydrogen, which has a nucleus only composed of a proton), the former being positively charged and the latter having no charge. The dance that these particles undergo will be the subject of our attention in a future arc, but, for now, let’s focus on the electron - the atom’s currency, as I’ve called it. You can think of these electrons as a mode of “communication” between atoms. Sometimes that communication can be a bit rocky - electrons are very finicky when it comes down to it. Your professors and teachers may have used words like “valence shell” and “orbital”, which sound downright scary if you’re uninitiated, but we'll take it from the top (and I promise to make this more painless than your instructors tried to).
Explosions occur as built-up energy is suddenly released.
In order to properly understand the atom, we have to start with an observation that holds true for every system in the universe - lower energy is the ultimate goal. Everything you see in the world follows this principle. It is why when a fast-moving car (the energy of motion) crashes, you hear sound (a type of energy) corresponding to the speed it was moving. Energy represents the stability of a system and the less of it you have, the more stable you are. Said another way, if a system built up energy and could not release it, for whatever reason, it would be considered unstable. That’s when you get explosions.
The Electric Force
The negative charge of an electron and the positive charge of a proton are keys to the electric force, which both keeps electrons apart and attract electrons to the nucleus. This force is a component of the electromagnetic force, one of the universe’s most fundamental forces that governs everything in the realm of electricity and magnetism.
There is a formula out there that nicely explains the electric force - Coulomb’s Law. We will go through the terms of this equation in full.
Coulomb’s Law. The force, F, has the unit of newtons, named after Sir Isaac Newton, who created the foundational equation for force.
First, most notably is k, the Coulomb Constant. A constant, if you are unaware, is a fixed value, usually represented by a letter or sign. The constant in this equation, k, will always represent a value of 9 x 109 N*m2/C2. (N is newton, a unit of force, m is meter, a unit for distance and C is coulomb, a unit for charge).
Next, we have both q values. These represent the quantity of the charges between the two particles being compared. These charges have the same value, but opposite signs, according to if the charge is a proton or electron. There can be more than the two q values shown in the equation above.
Last is r, or the distance between the particles.
Now, these values, after being determined experimentally, can be put into the above equation and an electric force, F, can be quantified, but the important part here is the sign of the force, or whether it is positive or negative. If the force is positive, the two particles repel each other, and if it is negative, the two attract each other. Electrons that are near each create a positive electric force, meaning they repel, and their energies rise when near each other. That, as we know, is no good.
The higher the repulsive force, the more likely they are to distance themselves in order to lower that total energy. The attractive force between the electrons and the protons, however, is strong enough to keep everything together. This leads to particular areas within an atom where the electron must be for the sake of stability. We call those areas orbitals, which we will certainly discuss later as we build more knowledge in the realm of quantum mechanics.
This foundation gives us enough of an understanding to clear up one of science’s most well-known atomic models.
Models of the Atom
The Planetary and Electron Cloud Model
Image via Byju’s
Without a doubt, this image looks familiar to you. I hate to burst bubbles (except in cases like this), but this classic atomic model theorized by Ernest Rutherford, known as the “planetary model”, is actually an inaccurate representation of the atom. Electrons have quantum mechanical properties that make their exact positions impossible to identify. In actuality, we can only tell where an electron probably will be. So, a more accurate representation looks like this:
Image via Couts G8 Class
This model, the Electron Cloud model, is brought to you by Erwin Schrödinger. Yes, the same one with the cat and the box. Or was there a cat in that box…?
In any event, these probable locations fill out the space in our aforementioned orbitals, allowing those knowledgeable to identify an atom on sight. The cloud above, for example, is created within a lithium atom. There are many different orbital shapes created by electron clouds that we’ll cover when we get deeper into chemistry. For now, though, enjoy this sneak peek.
Image by Donald A. McQuarrie via “Quantum Chemistry”