Molecules

Goal of the class To understand molecules and how they are written Question of the day: What is the subscript used for? Previous Answer: New Term – No previous question Previous question: None

Molecules Bonding occurs when atoms take or share valence electrons When atoms share electrons, they become molecules Can be same the element (N2) Different elements (CO2) Molecules have no limits to the number of atoms that are bonded together https://folding.stanford.edu/

Molecular Properties Once molecules are bonded together they have different properties than individual atoms Example: water (H2O) has very different properties than hydrogen or oxygen Atoms bonded together undergo a chemical change Hardened steel, like in bicycle locks.

Chemical Formulae Chemical formulas will use the atomic symbols to show which atoms are in a molecule Example: CCl4 (carbon tetrachloride) It has one carbon atom and four chlorine atoms The small number near the elements is the subscript It shows the number of atoms that are bonded Cl C Sub / superscript Repeating units Car not to mistake this for C and I instead of Cl

Ions Ions don’t form molecules They can stick together with other ions or molecules some ions can be made of more than one atom Example: Hydronium H3O+ or Hydroxide OH- ions Hydronium ion It has one more proton than electrons in the molecule

Naming Molecules follow simple naming system with the subscript Mono- means one Di- means two Tri- means three Negative ions (anion) always end with –ide Example: Sodium and chlorine ions gives sodium chloride Tetra = 4 Penta = 5 Suffix means afterwards

Vocabulary Molecule – The smallest particle of a compound that retains its chemical properties; two or more atoms held together by chemical bonds Subscript – A type of lettering form that is written lower than the things around it.

Homework Please read Chemical Interactions textbook pages 25, 48-51 Please complete Chemical Interactions workbook page 16. http://phet.colorado.edu/en/simulation/build-an-atom