Kinds of matter
How many kinds of matter are there? So many that if you started to count
them, you probably would never finish!
But if you could sort out the atoms in all of that matter, you would
find that there are only about a hundred kinds. Each of the hundred
kinds of atoms has a nucleus, or center, of a different size, and a
different number of electrons.
Some kinds of matter are made up of only one kind of atom. These kinds
of matter are called elements [(ehl]{.smallcaps} uh muhnts). Gold is
an element—a piece of pure gold is made up of just gold atoms. Iron is
an element, too—it is made up of just iron atoms.
sulfur
But most kinds of matter are made of different kinds of atoms joined
together. These kinds of matter are called compounds
[(kahm]{.smallcaps} powndz).
Water is made of an element called oxygen [(ahk]{.smallcaps} suh juhn)
and an element called hydrogen [(hy]{.smallcaps} druh juhn). By itself
oxygen is an invisible gas—you can’t see it. So is hydrogen. But when
they join, they make a liquid you can see, feel, and pour—water.
Compounds can have many more kinds of atoms. And the atoms can be put
together in different ways. But all compounds are made from two or more
of the hundred or so kinds of atoms we know.
Sulfur is a soft, yellow element and copper is a shiny, red-brown
element. But when copper atoms and sulfur atoms join together, they form
a different kind of material—a black, powdery compound called copper
sulfide.
copper sulfide
