An Element Is a Part of Matter Made of Only One Type of Atom

Compound Notes

An element is a part of matter made of only one type of atom. Elements can be found in nature or made in a laboratory. All elements are listed on the Periodic Table of Elements according to the number of protons in the nucleus. The smallest part of an element is called the atom.

A compound is a form of matter that is made when two or more elements combine to form a chemical bond. The atoms become linked and can only be separated by a chemical reaction. Millions of compounds can be made from combinations of elements. Some common examples of compounds include salt, water, sugar, baking soda and vinegar. A molecule is the smallest part of a compound. Inside a salt shaker, there are millions of molecules of salt.

A compound is usually much different from the elements that make it up. For example, salt is a compound formed when sodium and chlorine chemically combine. Sodium is a gray solid that will catch on fire when placed in water. Chlorine is a greenish gas with a strong odor. However salt does not react with water and has no odor. The reason for this is when the atoms are chemically linked, they lose their original properties.

A chemical symbol is the abbreviation used to represent an element. A chemical formula is the abbreviation used to represent a compound. It is made up of symbols of the elements and the number of atoms of each element that are in the compound.

The chemical formula for water is H2O. The 2 after the H means there are two atoms of hydrogen. When there is no number written after a chemical symbol, there is one atom of that element. So in a water molecule, there are 2 atoms of hydrogen and 1 atom of oxygen. Another example of a compound is propane with a formula of C3H8, this means there are three carbon atoms and eight hydrogen atoms.

1. Define element: ______

2. Define compound: ______

3. Define molecule: ______

4. Give 2 examples of compounds ______

5. Describe what happens to an element’s properties when it joins with other elements to form a compound. 6. What is the difference between a chemical symbol and a chemical formula?

7. The formula for baking soda is NaHCO3. List the elements and the number of atoms of each element found in baking soda.

Element Name # of atoms Na - H - C - O -

8. Listed below are some compounds with their chemical formulas. For each formula, list the components of each compound.

Chalk CaCO3 Calcium – 1, Carbon – 1, Oxygen – 3

Salt NaCl ______

Sulfuric Acid H2SO4 ______

Sand SiO2 ______

Sugar C6H12O6 ______

Rust Fe2O3 ______

Hydrogen peroxide H2O2 ______

Aspirin C9H8O4______

Iron Pyrite (Fool’s Gold) FeS2______

9. Why is a chemical formula useful for scientists?

10. If salt is made of sodium and chlorine and chlorine is what they use to kill germs in a pool, why does salt not kill germs?