A. Chemical Compound: two or more atoms chemically combined. II. Compounds & Bonding A. Chemical Compound: two or more atoms chemically combined. 1. Expressed as a 3-part molecular formula: Symbol Coefficient Subscript Example: To calculate the total numbers of individual atoms, multiply the coefficient by the subscripts. In the 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. 2 Glucose molecules: 2C6H12O6 C: H: O: 12 24 b. 6 Methanes: 6CH4 C: H: 6 24

c. 1 Ammonium Phosphate: (NH4)3PO4 12 1 4 When a group of elements are inside of parentheses with a subscript outside, multiple the subscript outside by the subscript of each element to calculate total number of each atom (distributive property) d. 2 Iron Sulfates: 2Fe2(SO4) 3 Fe: S: O: 4 6 24

B. Chemical Bonds There are 2 main types of chemical bonds that hold molecules together (Chemical bonds require and store energy) 1. Covalent Bond: 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. Structural Formula Example 1: H2O (water)

H O H O H O H Represents 1 pair of shared electrons Structural Formula

Example 2: CH4 (methane) *Draw the bonded Bohr Diagram, Lewis Structure, and Structural Formula of methane.

electrons are transferred from one atom to another, creating ions. 2. Ionic Bond: electrons are transferred from one atom to another, creating ions. a. Ion: an atom that has lost or gained electrons thus having a positive or negative charge. Lost e- = positive ion Gained e- = negative ion

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

Neutral Sodium Atom: Protons: +11 Electron: -11 ----------------------- Charge: 0 Neutral Chlorine Atom: Protons: +17 Electron: -17 ------------------------ Charge: 0 Sodium Ion: Protons: +11 Electron: -10 ------------------ Charge: +1 Chlorine Ion: Protons: +17 Electron: -18 ------------------ Charge: -1

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

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

Mg Cl Cl

weak attraction between polar molecules that are very close together C. Hydrogen Bonds: 1. 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. 2. The positive pole of one molecule is attracted to the negative pole of another.

D. Writing chemical equations: Products Reactants Yields 6CO2 + 6H2O C6H12O6 + 6O2 6 Carbon 12 Hydrogen 6 Carbon 6 Oxygen 12 Oxygen 12 Oxygen 6 Oxygen 12 Hydrogen 18 Oxygen total 18 Oxygen total *Whatever goes into the reaction (reactants) must come out (products).  You will have the same number of atoms on either side of the equation!

_____ H2 + _____ O2  _____H2O 4 H O 2 1 4 2