What are atoms, elements, molecules, and compounds?

Atoms Definition: An atom is the smallest particle of an element that still has the properties of that element. All matter is made of atoms, even you.

Atoms Atoms are structures too small for us to see, even with aid of a microscope. Because we can’t see atoms, we use models to help us study and understand them

Atom model We often use circles to represent atoms and put them together to represent molecules. Some use a bar or a line to represent the bonds between the atoms and some don’t. N N

Elements O N Definition: An element is a substance made of only one kind of atom. Elements can be arranged to form new substances. O N O N

Molecule Element Definition: A molecule is formed when 2 or more atoms bond together. If a molecule is made up of only 1 kind of atom we call it an element. If the molecule is made up of 2 or more kinds of atoms we call it a compound. Compound

Molecules Atoms of elements often bond together to form molecules. Atoms of oxygen bond together to form oxygen molecules or O2. O O O O

Element Molecules Hydrogen molecules are formed when 2 hydrogen atoms bond together. H H Sulfur molecules are formed when 8 sulfur atoms bond together. This molecule is made of only 1 kind of atom so it is considered an element.

Compounds Definition: A compound is two or more elements joined together by a chemical bond. Water is an example of a compound. Each molecules is made up of 1 oxygen atom and 2 hydrogen atoms.

Sugar Compound The simple sugar glucose is a compound made up of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. O C C C C C C

Glucose Glucose is a product of photosynthesis. Atoms are rearranged to produce oxygen and glucose. O + +

Compound Properties The properties of a compound are often very different from the elements they are made up of. For example, at room temperature hydrogen and oxygen are both gases but water is a liquid. 2 Hydrogen + Oxygen “yields” Water (hydrogen oxide) +