Presentation on theme: "Compounds Chemistry Lecture #3 Elements Entangled Element – the simplest type of pure substance Pure substances that are made of more than one element."— Presentation transcript:
The properties of the elements that make up a compound are often quite different than the compound itself. Compounds are made of molecules. A molecule is made of two or more atoms chemically bonded together.
Chemical Formulas Chemical Formulas are a shorthand way of representing chemical substances. H 2 O = chemical formula for water (two hydrogen atoms + 1 oxygen atom)
Some more chemical formulas: NH 3 (ammonia) = 1 nitrogen atom + 3 hydrogen atoms C 3 H 7 OH (rubbing alcohol) = 3 carbons + 7 hydrogen + 1 oxygen + 1 hydrogen AgNO 3 (silver nitrate) = 1 silver + 1 nitrogen + 3 oxygen atoms
There are formulas that represent a molecule of an element. Example: In nature, oxygen occurs as a molecule that contains 2 oxygen atoms bonded together. O 2 subscript indicates 2 atoms of oxygen (H 2 = hydrogen, N 2 = nitrogen, F 2 = fluorine, Cl 2 = chlorine)
Equations During a chemical reaction, substances are changed into new and different substances through a rearrangement of their atoms. C + O 2 CO 2 This description of a chemical reaction using symbols and formulas is called a chemical equation.