Science “Matters”:
Atoms and Molecules
Have you ever built something with Lego’s? You start by dumping all of the Lego
blocks onto the floor. There are many different sizes and shapes and colors of
Lego’s. Some of them are the same, but many are different. You can build a
shape out of one kind of Lego block, or you can build a castle using all of the
different Lego pieces together.
Lego blocks are a lot like atoms. Atoms are the building blocks of matter. Atoms
join together to “build” matter. Matter can be very simple—just like building a
shape with only one kind of Lego block. Matter can also be very complicated—
just like building a castle from a set of Lego’s.
You have already learned that atoms are the smallest unit of matter. Are atoms
as small as anything can be? Atoms are the smallest piece of matter that can be
separated. All atoms are made of three particles called: protons, neutrons and
electrons. These three particles are always found together.
Protons have a positive (+) charge. Electrons have a negative (-) charge.
Neutrons have neither a positive nor a negative charge. Neutrons received their
name because they have a neutral charge (0).
At the center of an atom is its nucleus. The nucleus is made of protons and
neutrons. Electrons move in a circle around the nucleus of the atom—much like
how the planets move in orbit around the sun. The drawing below shows an
atom, with protons shown in red, neutrons shown in black and electrons shown in
blue.
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Some atoms have room to hold more electrons around their nucleus. Some
atoms have more electrons than they need around their nucleus. Atoms will
sometimes join together and share electrons. When atoms share electrons, a
chemical bond occurs. A molecule is formed when two or more atoms share a
chemical bond. Sometimes, two or more of the same kind of atom form a
molecule. This is called an element. When two or more different kinds of atoms
form a molecule, it is called a compound. The drawing below shows a
compound, two different atoms that share a chemical bond.
There are many different compounds. Some are very simple. Table salt is a
compound containing one atom of sodium and one atom of chlorine. Water is
also a simple compound. Water is made of two atoms of hydrogen and one atom
of oxygen.
Other compounds are very complex. They are made of many different atoms.
The molecules that make up our blood, skin, muscles and organs are very large
molecules made of many atoms. Some of the most common atoms in our bodies
are: carbon, nitrogen, oxygen, and hydrogen.
Ninety two different elements are found on Earth. Man has made almost twenty
more elements. All of the elements are listed on the Periodic Table of the
Elements. The Periodic Table puts all of the elements in order from the smallest
to the largest. It also organizes the elements. One of the ways that the Periodic
Table organizes the elements is by separating metals and non-metals.
It is amazing that all atoms are made of only protons, neutrons and electrons.
Atoms join together to make molecules. Molecules join together to make up the
matter that everything in our universe is made of.