Bonding and not in the getting-to-know-each-other sense

What is a Bond? Bond: (also known as a chemical bond): the force that holds 2 or more atoms together and makes them function as a unit.

Why bond? Every atom’s goal is to have a full outer shell! They will do whatever it takes to fulfill their goal…steal… give it up… or share…

Types of Bonds: Ionic Ionic Bond: bond that occurs between two oppositely-charged ions. –We know opposites attract, so when we have a positive cation (Na + ) and a negative anion (Cl - ), they stick together.

Types of Bonds: Covalent Covalent Bond: (or nonpolar colvalent): bond that occurs when two atoms share electrons They don’t have enough pull on the electron to fully steal it, so they have to share.

FACTS.. Covalent bonds usually form between the seven diatomic elements: N, O, F, Cl, Br, I, H –Diatomic = 2 of them stuck together The combination of elements formed by a covalent bond results in a molecule.

Types of Bonds: Polar Covalent Polar Covalent Bond: bond that occurs when 2 atoms share electrons, but one has more pull on electrons… More ELECTRONEGATIVITY!!

Look at Electron Clouds Shared equally Not shared Unequal sharing ( )

How Do We Know What Happens? If the difference between the electronegativities is LARGE, it is IONIC. –**mostly metal-to-nonmetal bonds If the difference between the electronegativities is ZERO, it is COVALENT. –**mostly the same element If the difference between the electronegativities is INTERMEDIATE, it is POLAR COVALENT. –**mostly 2 different nonmetals

Practice! Tell whether the following are ionic, covalent, or polar covalent bonds AND WHY: 1. S-S 2. S-O 3. S-H 4. S-K

Check It! Tell whether the following are ionic, covalent, or polar covalent bonds AND WHY: 1. S-S: covalent (same element) 2. S-O: polar covalent (2 nonmetals) 3. S-H: polar covalent (2 nonmetals) 4. S-K: ionic (nonmetal-metal)

Practice with a Partner! 7 minutes to fill out the types of bonds. Yes, I’m going to grade it.

Using Lewis Dot Structures We can show the movement or sharing of electrons with Lewis Dot Structures. I know that the Lewis Dot Structure for sodium is: And I know that the Lewis Dot structure for chlorine is: So I can show Cl stealing an electron:

How NaCl is Formed Ionic bonding between the positive Na and the negative Cl keep them stuck together.

How CaCl 2 is formed Since Ca is giving away 2 electrons, it needs to find 2 Chlorines…each Cl can only take one electron

Practice with a Partner! 7 minutes to draw the losing/stealing of dots like what just happened. Yes, I’m going to grade it.

What if They Have to Share? Let’s look at chlorine gas, Cl 2 … I know the Lewis Dot Structure for chlorine is: So I can use the dots to show sharing:

Lewis Dots for Cl 2 Each Cl atom now has 8 valence electrons! --OR-- Shared pairs of electrons can be written as a straight line

How do we draw Lewis Dot Structures??? 1.Find the total # of valence electrons. 2.Use 1 line to show pairs of bonding electrons. 3.Fill in any extra electrons as dots. 4.Make sure each atom has 8 valence e -. Note: Hydrogen likes only 2 electrons. Why? 2 is enough to fill the 1 st energy level! (1s 2 )

Let’s See Water, H 2 0 We have 2 H atoms and each one has 1 valence electron… H: 2atoms x 1ve - = 2 valence electrons. O: 1atom x 6ve - = 6 valence electrons. Add them together and we have 8 e - ! –Draw a line for each shared pair: H-O-H –That uses 4; we have 4 left to put around O…

Practice! Draw the structure for: 1.Cl 2 O 2.SiF 4

Check It! Draw the structure for: 1.Cl 2 O Cl: 2atm x 7ve - = 14ve - O: 1atm x 6ve - = 6ve - =20ve - 2.SiF 4 Si: 1atm x 4ve - = 4ve - F: 4atm x 7ve - = 28ve - =32ve - Cl—O—Cl

Practice with a Partner! 7 minutes to draw the sharing of dots like what just happened. Yes, I’m going to grade it.

Sharing More Than 1 Pair Sometimes atoms need to share more than 1 pair of electrons to have a complete octet (8 e - in outer shell). This leads to double or triple bonds!

Double Bonds Double Bonds: occur when atoms share 2 pairs of electrons. –Ex. Carbon Dioxide, CO 2 C: 1 atom x 4 v.e - = 4 v.e - O: 2 atoms x 6 v.e - = 12 v.e - = 16 e - total

CO 2 Lewis Structure Here each Oxygen has 8 valence e -, BUT Carbon only has 4. 

So we move another pair in the middle to share with carbon…. CO 2 Lewis Structure

Here each Oxygen has 8 valence e -, AND Carbon has 8, too.

Triple Bonds Triple Bonds: occur when atoms share 3 pairs of electrons. Like with double bonds, atoms are simply trying to get a full octet

Practice with a Partner! Draw the sharing of electrons like what just happened.