Chemical Bonds Why Atoms Combine?

Why Would Elements Want to Combine? Most elements are unstable The only stable elements are the _____? So elements combine to become _____?

Formulas Formulas are used to represent a shorthand form of a compound H 2 0 is the formula for water This tells us there are 2 hydrogen atoms and 1 oxygen atom in this compound

Rules for Writing Formulas The cation USUALLY comes first The anion USUALLY comes last Cation- positive charged atom Anion- negative charged atom

Which is Which? Sodium is the _______? Chlorine is the _______? Calcium is the _______? Oxide is the ________?

Stable Elements Unless the element is a noble gas, to achieve a stable form of itself it needs a full outer shell of electrons (8 electrons) To do this we combine the right number of elements to become stable We always look to the charges of each of the elements

Let’s Try To Become Stable Combine sodium and chlorine Combine Chlorine with itself Two ions from opposite sides of the table form IONIC BONDS Which example from above is a compound with an ionic bond?

Continued Covalent bonds keep non-metals attached to each other Oxygen in our air is found as O 2 Oxygen bonds with a covalent bond

Ionic vs. Covalent Ionic compounds exchange electrons Covalent compounds share electrons

Covalent Bond (Copy)

Common Ionic Compounds NaCl KCl MgCl 2 MgO

Common Covalent Compounds CH 4 H 2 0 HCl O 2 N 2

Assignment Write the name for the following compounds: 1. LiBr 2. CaCl 2 3. AlCl 3 4. KI 5. MgF 2 Write the chem. Formula for the following: 1. Sodium chloride 2. Magnesium oxide 3. Cesium chloride 4. Iron (II) oxide 5. Tin (II) chloride

1 st Thing 1st Copy the list of Polyatomic Ions from the right What is a polyatomic ion? Poly means many Many atoms is the meaning Charge Name Formula 1+ Ammonium NH 4 1- Acetate C 2 H 3 O 2 Chlorate ClO 3 Hydroxide OH Nitrate NO 3 2- Carbonate CO 3 Sulfate SO 4 3- Phosphate PO 4

Binary Compounds We have been working mostly with binary compounds (bi-meaning two) NaCl is a binary compound Be sure to add –ide to replace the end of the second element (oxide, chloride)

Back to Polyatomic Ions The charge of the 1 st element must equal the charge of the polyatomic ion K(CO 3 )  Is this right? No, Why? K is a +1 and Chlorate is a –2 K 2 (CO 3 )  Is this right? Yes

Hydrates If water is part of an ionic compounds structure we call this a hydrate An example is Cobalt Chloride penta- hydrate This is written as CoCl5 H 2 0

Anhydrous This is the removal of that water Anhydrous means “without water”