Multiple Covalent Bonds  A covalent bond can share more than one pair of electrons. Example: Nitrogen that exists in the atmosphere is N 2

Unequal Sharing of Electrons  In a water molecule, oxygen pulls the electrons more strongly than the hydrogen atoms do. The electrons spend more time around the oxygen, which makes the oxygen have a partial negative charge, and the hydrogen atoms have a partial positive charge.

Polar or Nonpolar?  A polar molecule is one that has a slightly positive end and a slightly negative end. The overall charge of the molecule is NEUTRAL. Example: water  A nonpolar molecule is one where all the electrons are shared equally. Example: O 2 (Draw it!)

Binary Compounds  A binary compound is one that is composed of two elements. CompoundBinary Yes/No? N2N2 H2OH2O O2O2 HCl

Oxidation Numbers  An oxidation number tells you how many electrons an atom has gained, lost, or shared to become stable.

Compounds are Neutral  A compound needs the right number of positive ions and the right number of negative ions so the charges balance. Example: Na + Cl -  One positive ion and one negative ion…neutral compound. Example: How would you balance the compound calcium fluoride?

Finding a Common Multiple  Aluminum Oxide Aluminum oxidation number: ______ Oxygen oxidation number: ______ How can you get this compound to balance???  Find a common multiple of each number…in this example the common multiple is: ______.

Writing Formulas  Rules: 1. Write the symbol of the element that has the positive oxidation number or charge. 2. Write the symbol of the element with the negative oxidation number. 3. The charge of one ion becomes the subscript of the other ion.  Example:

Let’s Do an Example  Lithium Nitride  1. Li 1+  2. N ?  3. Li 1+ N 3-  4. Li 3 N

More Practice  1. What is the formula for lead (IV) phosphide?  2. What is the formula for iron (III) oxide?

Writing Names  1. Write the name of the positive ion.  2. Look at table 2, pg. 616  3. Write the root name of the negative ion.  4. Add the ending “–ide” to the root name.

Writing Names Example:  What is the name of the compound CuCl? 1. Name of the positive ion in the compound: copper 2. See table 2…is that element on the table?  Yes! Copper I and Copper II, which should we use??? 3. Write the root name of the negative ion: chlor 4. Add the ending –ide to the root: 5. Write the entire name:  Copper (I) Chloride

Compounds with Complex Ions  Polyatomic Ions- a positively or negatively charged, covalently bonded group of atoms. Example: Baking Soda (NaHCO 3 ) See Table 4, pg. 619 (and table in your notes!)

Writing Names with Polyatomic Ions  You will need to use table 4, pg. 619! Example: Sr(OH) 2  1. Write the name of the positive ion Strontium  2. Use table 4, pg 619 to find the name of the negative ion. (OH) is hydroxide  3. Put it all together! Strontium Hydroxide

Writing Formulas with Polyatomic Ions  Write the formula for ammonium phosphate (See table 4, pg 619)  1. What is the positive ion? NH 4 + (ammonium)  2. What is the negative ion? PO 4 3-  Balance the charges to make the compound neutral: NH PO 4 3- = (NH 4 ) 3 PO 4

Hydrates  A hydrate is a compound that has water chemically attached to its ions and written into its chemical formula. Example: Cobalt chloride hexahydrate  Is pink when water is present  Turns blue when it dries.

Naming Binary Covalent Compounds  Remember that covalent compounds are those formed between non-metals.  Some pairs of nonmetals can form more than one compound with each other. Example: Nitrogen and Oxygen can form: N 2 O, NO, NO 2, N 2 O 5 All these would be nitrogen oxide!

Using Prefixes  Prefixes are used to indicate how many atoms of each element are in a binary covalent compound. Example:  N 2 O (dinitrogen oxide)  NO (nitrogen oxide)  NO 2 (nitrogen dioxide)  N 2 O 5 (dinitrogen pentaoxide)