Atoms — Definition & Overview

The Smallest Unit of an Element

This is an atom, one of the particles that make up everything.

Atoms are incredibly small, smaller than we can really comprehend.

They are the smallest unit of an element that still has the properties of that element. They cannot be broken down into other substances. They are made of three types of the subatomic particles called protons, neutrons, and electrons. If you cut an atom in half, you'll just have some subatomic particles that no longer have the properties of the element they represent.

Protons are positively charged particles while neutrons are neutral (they have no charge). These two types of particles are found in the center of the atom, called the nucleus. Electrons are negatively charged and much, much smaller than the protons and neutrons.

Elements have the same number of protons and electrons. This makes them neutral, so they have no charge. That's because the electrical forces between the positively charged nucleus and the negatively charged electrons cancel out.

The Nucleus

Very strong forces bind protons and neutrons together to make up the nucleus, or core, of the atom. The nucleus makes up most of the mass of an atom.

Here's a trick to remember which subatomic particle in the nucleus is which:

• P = Proton = Positive charge
• N = Neutron = Neutral charge

The electrons constantly orbit the nucleus at break-neck speeds. Because they are negatively charged, they are attracted to the nucleus. However, the great speed they travel at keeps them orbiting outside the nucleus. You can think of it like satellites orbiting the earth. You think they should come crashing down, but they are moving fast enough to prevent it.

Representing Protons

The number of protons determines the atomic number of the atom, which is how we identify elements. We'll get more into this later when we discuss elements and the mass number.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Atom}}$ : The smallest particle of an element that has the properties of that element

$\color{#8925AE}{\text{Nucleus}}$ : The positively and neutrally charged subatomic particles, protons and neutrons, located in the center of the atom

$\color{#8925AE}{\text{Electron}}$ : The mind-bogglingly small, negatively charged subatomic particles that orbit the nucleus

$\color{#8925AE}{\text{Proton}}$ : The positively charged subatomic particles located in the nucleus

$\color{#8925AE}{\text{Neutron}}$ : The neutrally charged subatomic particles located in the nucleus

$\color{#8925AE}{\text{Element}}$ : A substance that can not be broken down into other substances. All atoms of an element have the same atomic numbers

$\color{#8925AE}{\text{Atomic Number}}$ : The number of protons in the nucleus, which lets us identify which element it is

What Is an Atom?

All matter is made up of teeny, tiny atoms (pronounced like "Adam's").

Atoms are way too small to see with the naked eye; they're even too small for most microscopes.

The University of Utah has an amazing interactive website that shows the size of a carbon atom. You can drag the little box at the bottom of the screen to the right to see how atoms compare to the sizes of things like coffee beans, skin cells, and bacteria.

The main ideas to get here are the following: all matter is made up of atoms and atoms are really, really small.

What Are the Parts of an Atom?

Atoms themselves are made of even smaller particles. These are called the subatomic particles.

There are three subatomic particles you'll need to know about:

The nucleus is the red and blue blob in the middle of the atom in the picture above. The nucleus is generally considered the center of the atom while the electrons float around the outside.

An important thing to remember is that atoms are electrically neutral (they should have no net charge). To be electrically neutral, atoms have the same number of protons and electrons. Since protons are positively charged and electrons are negatively charged, having the same number of them means that their charges cancel out.

You can find out the number of protons an element has by looking at the Periodic Table of the Elements.

Vocabulary:

1. Atom
2. Subatomic particles
3. Nucleus
4. Proton
5. Neutron
6. Electron
7. Periodic table

Properties of Atoms

What Is an Atom?

An atom is the smallest unit of matter that still keeps the chemical properties of an element. For example, a pound of gold has the same chemical properties as a single atom of gold. However, if you break the atom apart, it will no longer behave like gold.

What Are Atoms Made Of?

The protons and neutrons clump together to make what is called the center of the atom, or nucleus.

Protons have a positive charge. Neutrons have no charge and are neutral. Electrons have a negative charge and travel very quickly in orbitals around the nucleus. They are much, much smaller than protons and neutrons.

If there is an equal number of electrons and protons, then the atom has no electric charge. When an atom has a charge, it is called an ion.

• If there are fewer electrons than protons, the atom has a positive charge and is called a cation.

• If there are more electrons than protons, the atom has a negative charge and is called an anion.

Atoms usually have the same number of protons and neutrons. If an atom adds to or removes neutrons from the nucleus, it becomes an isotope.

(Video) How Small Is an Atom? Spoiler: Very Small

by Kurzgesagt – In a Nutshell

This video helps us visualize just how tiny an atom really is.

It describes the structure of an atom, including protons, neutrons, and electrons. It also shows us what an atom might actually look like.

Lastly, we learn how the basic component of atoms can create many different elements.