D. Chemical Compounds: two or more atoms chemically combined. 1. Expressed as a 3-part molecular formula: a)Symbol b)Coefficient c)Subscript Example: To calculate the total numbers of individual atoms, multiply the coefficient by the subscripts.  In the 3 molecules above, we have 6 hydrogen atoms and 3 oxygen atoms.

2. More Examples: find the total number of each atom in the molecules below. a) Glucose: 2C 6 H 12 O 6 b) Methane: 6CH 4 C: H: O: C: H:

3. The main types of chemical bonds include covalent and ionic bonds. a)Covalent Bonds: atoms share their valence (outer-most) electrons. *The number of valence electrons determines how many bonds an atom can make. *Atoms “want” to fill their valence shells. Example 1: H 2 (hydrogen gas) Lewis Structure Structural Formula

Example 2: CH 4 (methane) Lewis Structure Structural Formula

Example 3: H 2 O (water) Lewis Structure Structural Formula

Example 4: HCl (hydrogen chloride) Lewis Structure Structural Formula

b) Ionic Bonds: electrons are transferred from one atom to another, creating ions. 1)ion: an atom that has lost or gained electrons thus having a positive or negative charge. Lost e - = positive ion Gained e - = negative ion

2) The opposite charges between ions create a strong attraction in ionic bonding. Example: NaCl (table salt) Opposites attract, BABY! Na Cl Hey! Could you spare an electron? Sure why not! Thanks! You sure you don’t mind? I didn’t want to be a bother! Don’t be so negative! Sorry – I can’t help it! You sure it’s ok? I’m positive! I suddenly find myself attracted to you! Me too! I feel like we’re bonding! + -

Cl Na Cl + _ Put brackets around the atom that received the electron(s).

Mg Cl Give me yo electron, FOOL! Me too, SUCKA! Hey! Those are mine! Now I’m going to keep an ion both of you! +2 --

c) Hydrogen Bonds: attraction between polar molecules that are very close together *Polar Molecules form when electrons are not shared equally between atoms in a molecule, so poles (opposite charges) form at either end of the molecule. The positive pole of one molecule is attracted to the negative pole of another. Opposites attract, BABY!

4. Writing chemical equations: Reactants Yields Products C 6 H 12 O 6 6H 2 O6CO 2 6O 2 ++ *Whatever goes into the reaction (reactants) must come out (products).  You will have the same number of atoms on either side of the equation! 6 Carbon 12 Oxygen 12 Hydrogen 6 Oxygen 18 Oxygen total 6 Carbon 12 Hydrogen 6 Oxygen 12 Oxygen 18 Oxygen total