Elements and Compounds Foothill Chemistry

Vocabulary Element Atomic Number Chemical Symbol Substance Compound Chemical Change Chemical Formula Molecule

Element A substance that cannot be separated or broken down into simpler substances by chemical means All atoms of an element have the same atomic number Elements are represented on the periodic table by their chemical symbol

Chemical symbols Chemical symbols are 1-2 letter “abbreviations” for the element The first letter (if there is more than one) is always capitalized The second letter is not capitalized

Substance A substance can be represented by a chemical formula to represent the atoms that it contains All of the molecules are the same No matter how large or small of a sample you have, the molecules will be the same molecule A molecule is the smallest unit of a substance that keeps all of the physical and chemical properties of that substance

Chemical Compound Substance that contains more than one type of atom Has to have at least two different atoms The atoms have to be chemically bound together The ratio of the atoms is shown by the subscripts in the chemical formula

Chemical Formula A combination of chemical symbols and numbers to represent a substance Can represent an element or a compound Does not represent a mixture H2O - Water NH4 - Ammonia CH3OH – Methyl Alcohol SO2 – Sulfur Dioxide

Element vs. Compound One type of atom Diatomic elements have two of the same atom in their molecules More than one type of atom, chemically bound

Chemical Reaction The process by which one or more substance change to produce one or more different substances Reactants – Molecules you start with Products – Molecules you get from the reaction

Mixture No chemical symbol to represent the mixture There is more than one type of molecule found in a mixture Multiple substances are found in a mixture

Classifying Matter