1 chapter 8.2 covalent bonding chemistry los altos high school darren dressen, m.s
TRANSCRIPT
![Page 1: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/1.jpg)
1
Chapter 8.2
“Covalent Bonding”
Chemistry
Los Altos High School
Darren Dressen, M.S.
![Page 2: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/2.jpg)
2
Section 8.2The Nature of Covalent Bonding
OBJECTIVES:– Learn that a chemical bond contains two
electrons– To understand single, double, and triple
bonds in a covalent compound– How to represent molecules as Lewis
structures (start with some examples, we will get more practice)
![Page 3: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/3.jpg)
3
Covalent BondsThe word covalent is a
combination of the prefix co- (from Latin com, meaning “with” or “together”), and the verb valere, meaning “to be strong”.
Two electrons shared together have the strength to hold two atoms together in a bond.
![Page 4: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/4.jpg)
4
How does H2 form?
The nuclei repel each other, since they both have a positive charge (like charges repel).
++
(diatomic hydrogen molecule)
+ +
![Page 5: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/5.jpg)
5
How does H2 form?
++
But, the nuclei are attracted to the electrons
They share the electrons, and this is called a “covalent bond”, and involves only NONMETALS!
![Page 6: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/6.jpg)
6
Covalent bonding Fluorine has seven valence
electrons (but would like to have 8)
F
![Page 7: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/7.jpg)
7
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven
F F
![Page 8: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/8.jpg)
8
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven By sharing electrons…
F F
![Page 9: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/9.jpg)
9
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven By sharing electrons…
F F
![Page 10: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/10.jpg)
10
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven By sharing electrons…
F F
![Page 11: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/11.jpg)
11
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven By sharing electrons…
F F
![Page 12: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/12.jpg)
12
Covalent bonding Fluorine has seven valence
electrons A second atom also has seven By sharing electrons…
F F
![Page 13: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/13.jpg)
13
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons…
…both end with full orbitals
F F
![Page 14: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/14.jpg)
14
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full orbitals
F F8 Valence electrons
![Page 15: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/15.jpg)
15
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full orbitals
F F8 Valence electrons
![Page 16: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/16.jpg)
16
A Single Covalent Bond is... A sharing of two valence electrons. Only nonmetals and hydrogen. The most common bond. Represented by a single line
between two atoms
![Page 17: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/17.jpg)
17
Our First Lewis Structure: Water
H
O
Each hydrogen has 1 valence electron
- Each hydrogen wants 1 more
The oxygen has 6 valence electrons
- The oxygen wants 2 more They share to make each
other complete
![Page 18: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/18.jpg)
18
Water Put the pieces together The first hydrogen is happy The oxygen still needs one more
H O
![Page 19: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/19.jpg)
19
Water So, a second hydrogen attaches Every atom has full energy levels
H OH
Note the two “unshared” pairs of electrons
![Page 20: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/20.jpg)
20
Another way of indicating bonds
Often use a line to indicate a bond Called a structural formula Each line is 2 valence electrons
H HO = H HO
![Page 21: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/21.jpg)
21
Multiple Bonds Sometimes atoms share more than
one pair of valence electrons. A double bond is when atoms share
two pairs of electrons (4 total) A triple bond is when atoms share
three pairs of electrons (6 total) Table 8.1, p.222 - Know these 7
elements as diatomic:
H2 N2 F2 O2 I2 Cl2 Br2
What’s the deal with the oxygen dot diagram?
![Page 22: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/22.jpg)
22
Dot diagram for Carbon dioxide CO2 - Carbon is central
atom ( more metallic ) Carbon has 4 valence
electrons Wants 4 more Oxygen has 6 valence
electrons Wants 2 more
O
C
![Page 23: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/23.jpg)
23
Carbon dioxide Attaching 1 oxygen leaves the
oxygen 1 short, and the carbon 3 short
OC
![Page 24: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/24.jpg)
24
Carbon dioxide Attaching the second oxygen
leaves both of the oxygen 1 short, and the carbon 2 short
OCO
![Page 25: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/25.jpg)
25
Carbon dioxide The only solution is to share more
OCO
![Page 26: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/26.jpg)
26
Carbon dioxide The only solution is to share more
OCO
![Page 27: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/27.jpg)
27
Carbon dioxide The only solution is to share more
OCO
![Page 28: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/28.jpg)
28
Carbon dioxide The only solution is to share more
OCO
![Page 29: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/29.jpg)
29
Carbon dioxide The only solution is to share more
OCO
![Page 30: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/30.jpg)
30
Carbon dioxide The only solution is to share more
OCO
![Page 31: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/31.jpg)
31
Carbon dioxide The only solution is to share more Requires two double bonds Each atom can count all the
electrons in the bond
OCO
![Page 32: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/32.jpg)
32
Carbon dioxide The only solution is to share more Requires two double bonds Each atom can count all the electrons in
the bond
OCO8 valence electrons
![Page 33: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/33.jpg)
33
Carbon dioxide The only solution is to share more Requires two double bonds Each atom can count all the electrons in
the bond
OCO8 valence electrons
![Page 34: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/34.jpg)
34
Carbon dioxide The only solution is to share more Requires two double bonds Each atom can count all the electrons in
the bond
OCO
8 valence electrons
![Page 35: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/35.jpg)
35
How to draw them? Use the handout guidelines:
1) Add up all the valence electrons.
2) Count up the total number of electrons to make all atoms happy.
3) Subtract; then Divide by 2
4) Tells you how many bonds to draw
5) Fill in the rest of the valence electrons to fill atoms up.
![Page 36: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/36.jpg)
36
Example NH3, which is ammonia N – central atom; has 5
valence electrons, wants 8 H - has 1 (x3) valence
electrons, wants 2 (x3) NH3 has 5+3 = 8
NH3 wants 8+6 = 14 (14-8)/2= 3 bonds 4 atoms with 3 bonds
N
H
![Page 37: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/37.jpg)
37
N HHH
Examples Draw in the bonds; start with singles All 8 electrons are accounted for Everything is full – done with this one.
![Page 38: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/38.jpg)
38
Example: HCN HCN: C is central atom N - has 5 valence electrons, wants 8 C - has 4 valence electrons, wants 8 H - has 1 valence electron, wants 2 HCN has 5+4+1 = 10
HCN wants 8+8+2 = 18
(18-10)/2= 4 bonds 3 atoms with 4 bonds – this will require
multiple bonds - not to H however
![Page 39: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/39.jpg)
39
HCN Put single bond between each atom Need to add 2 more bonds Must go between C and N (Hydrogen is full)
NH C
![Page 40: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/40.jpg)
40
HCN Put in single bonds Needs 2 more bonds Must go between C and N, not the H Uses 8 electrons – need 2 more to
equal the 10 it has
NH C
![Page 41: 1 Chapter 8.2 Covalent Bonding Chemistry Los Altos High School Darren Dressen, M.S](https://reader036.vdocuments.site/reader036/viewer/2022081518/55149da7550346d36e8b5868/html5/thumbnails/41.jpg)
41
HCN Put in single bonds Need 2 more bonds Must go between C and N Uses 8 electrons - 2 more to add Must go on the N to fill its octet
NH C