Chemical Bonding. I. Introduction A. Types of Chemical Bonds – forces that hold two atom together...

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Chemical Bonding

Transcript of Chemical Bonding. I. Introduction A. Types of Chemical Bonds – forces that hold two atom together...

Page 1: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Chemical Bonding

Page 2: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

I. Introduction

A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a

nonmetal 2. Covalent Bonds – occur b/w 2

nonmetals & in polyatomic ions a. Polar Covalent Bonds -

Page 3: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

B. Distinguishing b/w Types of Bonds 1. Electronegativity – ability of an atom to

attract electron’s to itself.

Page 4: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

2. Bond Polarity: You can use the element’s electronegativities to determine the polarity of the bond – Just find the difference b/w the 2 numbers

0 – 0.4 Covalent bond 0.41 – 0.99 Polar Covalent bond > 1.00 Ionic bond

Page 5: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Determine the Polarity!

1. H – O 2. C – N 3. K – F 4. S – O 5. Al - P

Page 6: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

What Polarity Looks Like

Page 7: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

3. Dipole Moments – When a bond is polar… 1 side of the molecule is more positive and the other side is more negative.

Why? Because the electrons are being pulled toward the more electronegative element.

Page 8: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Dipole Moments

Page 9: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Why is Water’s Dipole Moment So Important?

It has a huge affect on its properties! It’s so important, it has a specific name,

it’s called HYDROGEN BONDING.

It is crucial to life on Earth! Polar water molecules can surround &

attract positive & negative ions which allows materials to dissolve in water!

Page 10: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

It’s polarity also means that water molecules are attracted to each other

A LOT of ENERGY is needed to change H2O from a liquid to a gas because the attraction must be overcome to separate 1 H2O molecule from another.

So what?!?! This causes water on Earth, at Earth’s temperatures, to remain a liquid. OTHERWISE, it would all be a gas and the oceans would be empty!!!!

Page 11: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

II. Ionic Bonds

A. A strong bond caused by the transfer of electrons from a cation (metal) to an anion (nonmetal). 1. Why? The driving force behind this bonding is

that all elements want to have a completely filled outermost energy level! [OCTET RULE]

a.) These outermost electrons are called the VALENCE ELECTRONS

b.) Metals LOSE valence electrons to be stable. c.) Nonmetals GAIN valence electrons to be

stable.

Page 12: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Valence Electrons1e- 8e-

  2e- 3e- 4e- 5e- 6e- 7e-  

               

    2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e-            

          1e-         1e-              

                   1e-               

                                   

                                   

2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e- 2e-

                           

                           

Page 13: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.
Page 14: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Let’s try it!

1. Na and O 2. Al and F 3. Ca and S 4. Mg and P

Page 15: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

B. Ionic Bonding And Structures of Ionic Compounds 1. Ionic compounds are

a. very stable, huge amounts of energy necessary to break them apart

b. high melting & boiling points NaCl has a melting point = ~800°C

Page 16: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

2. Structures of Ionic Compounds a. When you write the formula for an ionic

compound, you are writing its empirical formula.

b. In reality, the actual solid contains tremendous amounts & equal numbers of cations and anions packed together so that the attractions b/w them are maximized.

1.) Remember that cations are always smaller than anions. WHY?

Page 17: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.
Page 18: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

III. Covalent Bonding

A. Sharing electrons! 1. All bonding involves valence electrons

ONLY!!!!!! 2. Covalent bonds occur when 2 atoms (usually

nonmetals) share electrons. 3. LEWIS STRUCTURE – a representation of a

molecule that shows how the valence electrons are arranged among the atoms in the molecule.

Thought up by G.N. Lewis while teaching a chemistry class in 1902.

Page 19: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

See attached page for writing Lewis Structures!

Page 20: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

B. Structures – VSEPR Model 1. Valence Shell Electron Pair Repulsion

Model a. Useful for predicting the geometric shape

of molecules formed from nonmetals! b. The structure around a given atom is

determined by minimizing repulsions between electron pairs.

Page 21: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Metallic Bonding

How atoms are held together in the solid. Metals hold onto their valence electrons

very weakly. Think of them as positive ions floating in

a sea of electrons!

Page 22: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Sea of Electrons!

Electrons are free to move through the solid.

Metals conduct electricity.

+ + + ++ + + +

+ + + +

Page 23: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Metals are malleable!

Hammered into shape (bend). Ductile - drawn into wires.

+ + + ++ + + +

+ + + +

Page 24: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Malleable Electrons allow atoms to slide by.

+ + + +

+ + ++ + + +

Page 25: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Alloys

Solutions made by dissolving metal into other elements- usually metals.

Melt them together and cool them. If the atoms of the metals are about the

same size, they substitute for each other Called a substitutional alloy

Page 26: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Metal A

Metal B

+

Substitutional alloy

Bronze – Copper and Tin

Brass- 60 % Copper 39% Zinc and 1%Tin

18 carat gold- 75% gold, 25%Ag or Cu

Page 27: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Alloys

If they are different sizes the small one will fit into the spaces of the larger one

Called and interstitial alloy

Page 28: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Metal A

+

Metal B

Interstitial Alloy

Steel – 99% iron 1 % C

Cast iron- 96% Iron, 4%C

Page 29: Chemical Bonding. I. Introduction  A. Types of Chemical Bonds – forces that hold two atom together 1. Ionic Bonds – occur b/w a metal & a nonmetal 2.

Alloys

Making an alloy is still just a mixture Blend the properties Still held together with metallic bonding Most of the metals we use daily are

alloys. Designed for a purpose