Major Bond Types COVALENT e- are shared between 2 atoms IONIC e- are transferred from one atom to another COVALENT e- are shared between 2 atoms

Formed between a metal and non-metal Formed between 2 non-metals When does it occur? IONIC Formed between a metal and non-metal COVALENT Formed between 2 non-metals

How does it hold atoms together? COVALENT Shared attraction for same e- (+nucleus pulls on e-) Polar: doesn’t share equally Nonpolar: shares equally IONIC Electromagnetic forces; cation/ anion (opposites attract)

"GENEROUS" NON-METALS METALS "GREEDY" with their electrons

What is an example? IONIC COVALENT

How to draw an Ionic Bond 1. Write the elements that you are combining

2. Do a Lewis Dot Diagram for each atom

3. Draw the arrow from the e- that are moving to their new location 3. Draw the arrow from the e- that are moving to their new location. Add the final molecule on the right side (don’t forget the charges)

How to draw a covalent bond 1. Draw the Lewis Dot Diagram of each atom

2. Put the pieces together like a puzzle. Recall: the goal is to get a full valence shell

Ionic Compounds (salts) Made up of positive and negative ions cations and anions a metal and a nonmetal Smallest repeating unit- formula unit

Properties of Ionic Compounds All are Crystalline solids - They have a regular repeating arrangement of ions in a rigid 3-D structure Ionic bonds are the strongest bonds, so these compounds have high melting points

Properties of Ionic Compounds This orderly arrangement of component ions produces the beauty of crystalline solids. The beauty of crystalline solids, such as these, comes from the orderly arrangement of their component ions.

More properties of ionic compounds Conducting electricity is allowing charges (electrons) to move. In a crystalline solid, the ions are locked in place so they can’t conduct electricity When melted or dissolved in water, the ions are free to move around and, therefore, conduct electricity Brittle solids at room temperature

Properties of Ionic Compounds Summary: Properties of Ionic Compounds Structure: Crystalline solids Melting point: Generally high Boiling Point: Electrical Conductivity: Excellent conductors, when molten and aqueous Solubility in water: Generally soluble

Properties of Molecular (Covalent) Compounds Tend to have low melting and boiling points Poor or nonconducting Have a molecular formula which shows type and number of atoms in a molecule Not necessarily the lowest ratio! Ex. C6H12O6 (Formula doesn’t tell you about how atoms are arranged)

Bond type by electronegativity Electronegativities are listed on pg 151 Difference Bond Type < 0.4 nonpolar covalent between 0.4 and 2.0 polar covalent > 2.0 ionic

Bond Polarity Examples: Cl2 HCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 NaCl 3.0-0.9=2.1 Ionic We should guess this because it’s 2 like atoms We should guess this because it’s 2 different non-metals We should guess this because it’s a metal & a non-metal