Now that we have studied the basics of the atom, we need to explain what the words element, molecule and compound mean.
The periodic table of the elements lists all the different types of atoms. Much in the same way that the alphabet lists all of the letters in your language. So why don’t we call it the periodic table of the atoms? Because one atom is one unit of its element in the same way that one fish is a single unit in a school of fish. If I have one, single hydrogen atom, I have an atom. As soon as I have 2 or more hydrogen, I now have the element of hydrogen. You can think of element as the plural of atom. So, once you have more than one atom, instead of saying “I have X number of hydrogen atoms in my beaker.” You say “I have the element of hydrogen in my beaker.” The word element is the name of a group made up of a single type of atom.
So what is a molecule? Very simple, a molecule is created whenever two or more atoms form a bond with each other. A bond is like two lego pieces that are snapped together and now form a single unit of two lego. An example of a chemical bond is the molecule of Hydrogen. In the atmosphere, almost all of the free floating hydrogen atoms snap together in pairs, forming a molecule of hydrogen with the abbreviation H2
Now, if we have a beaker with H2 molecules in it, we still have a beaker with the element of hydrogen in it. Just because the two individual hydrogen atoms are bonded into one molecule, we still have only one type of atom. A molecule does not change the fact that something is an element. Now, you may be wondering what happens when two different types of atoms snap together to form a molecule. The answer to that question brings us to our last term: compound.
A compound is a molecule made up of two or more different types of atoms. Two examples would be table salt (i.e.: Sodium Chloride) and Hydroxide molecules:
These molecules involve two different types of atom therefore we label them as being compounds.
Remember that a compound has to be a molecule. Two different types of atoms (i.e.: elements) floating around each other in the same beaker but not bonded together do not make your beaker filled with a compound. It is a beaker filled with two elements.