2. Chemical Bond  The attraction between atoms that holds them together and makes them function as a unit.

5. Ionic Bonds  An ionic bond is a transfer of electrons between a metal and a nonmetal.  Electrons are completely transferred from one atom to another.  They either lose or gain electrons and form ions.  The atoms are bound together by the attraction between the opposite charges.

6. Types of Ions  The metal donates electrons and becomes positively charged-cation  The non metal gains electrons and becomes negatively charged-anion  Example Example

7. Writing Formulas 1. Write the symbols of each element. 2. Put their charge in their upper right corner. 3. Crisscross the numbers down (Not the charges). Example: Write the formula for Magnesium Chloride. Mg Cl Mg +2 Cl -1 Mg Cl

8. Writing Formulas Practice Write the formula for: 1. Aluminum Bromide 2. Calcium Oxide 3. Calcium Nitride 4. Sodium Chloride 1. Al Br 2. Ca O 3. Ca N 4. Na Cl

10. Covalent Bonds  A covalent bond is the sharing of electrons between 2 nonmetals.  example example  Both of the nonmetals want to gain electrons so they will share electrons to fill their orbitals. **A complete outer orbital has 8 electrons.**

11. Types of Covalent Bonds  Non-polar: an electron is shared equally between the atoms. Electronegativity difference: 0-0.3 Ex: H 2  Polar: an electron is more attracted to one atom than to another. Electronegativity difference: 0.3-1.7 Ex: HCl

12. Electronegativity differences Non-polar bond: Ex: H2 2.1-2.1=0 Polar Bond: Ex: HCl 3.0-2.1=0.9

13. Lewis Dot for Covalent Bonds  Can also be used to show bonding between atoms.  Electrons are placed between the atoms and are represented by a pair of dots or a dash.  Each dash represents one pair of electrons, or one bond. H2OH2O The structural formula shows a shared pair of electrons by a dashed line.

14. Drawing Covalent Bonds  Example: CH 4  Example: NH 3

15. Multiple Bonds  A single covalent bond is formed for every pair of electrons shared between two atoms.  Some atoms can share multiple pairs of electrons, forming multiple covalent bonds. Single bond- 1 pair of electrons Double bond- 2 pair of electrons Triple bond- 3 pair of electrons  example example

16. Multiple Covalent Bonds Examples:  Oxygen has six valence electrons, so it needs two electrons to complete its octet. When two oxygen atoms bond, they share two pairs of electrons, forming two covalent bonds.

17. Extras  Diatomic molecule- is a molecule containing 2 identical atoms. Examples: H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2  Chemical Formula- represents the # of atoms of each element in a compound by using symbols and subscripts. Example: H 2 O H=2 O=1  Bonding Animation Bonding Animation

18. Cartoon courtesy of NearingZero.net