• SCOS 4.02: Evaluate evidence that elements combine in many ways to produce compounds that account for all living and nonliving things
• Students will be able to…– describe a compound and molecule.– explain that all matter is made of compounds.
• Atoms combine with other atoms to form a chemical bond.
• As atoms combine, new substances are made.
• EXAMPLE: Na + Cl = NaCl or table salt
Molecules• A molecule is made of two or more atoms
joined by a chemical bond. • The atoms can be the same or different.
Compounds
• A compound is made of two or more DIFFERENT elements chemically combined in a set ratio.
NaCl (table salt / sodium chloride)
Chemical Formula• A chemical formula represents a compound.• It shows the elements in the compound and
the ratio of atoms.
• EXAMPLE: H2O
• EXAMPLE: H2O2 (hydrogen peroxide)
Other Examples of Chemical Formulas
• CaCO3 (calcium carbonate) – found in chalk and shells of some animals
• C8H10N4O2 – caffeine
• HClO – bleach• MgSO4 – Epsom Salt
• NaHCO3 (sodium bicarbonate) – baking soda
What elements are inbaking soda (NaHCO3)?
A) hydrogen, oxygenB) soda, bakingC) sodium, hydrogen, carbon, oxygenD) nitrogen, aluminum, hydrogen, carbon,
oxygen
• Compounds have properties that are different from those of the uncombined elements.
Sulfur Silver Ag2S
• EXAMPLE: Sulfur and Silver combine to form Ag2S (silver sulfide), which is tarnish and black in color.
How do the elements bond?
• RECALL: Electrons orbit around the outside of an atom.
• Atoms tend to GIVE UP or ACCEPT electrons to create chemical bonds.
• Chemical bonds form when all atoms have filled their outer electron orbital.