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Covalent Bonding Skeleton Diagrams. Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology. Only the noble gases have exactly the correct number of electrons to fill their outermost s and p orbitals. All other atoms have to lose, gain or share

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covalent bonding skeleton diagrams

Covalent BondingSkeleton Diagrams

Edward A. Mottel

Department of Chemistry

Rose-Hulman Institute of Technology

slide2

Only the noble gases have exactly the

correct number of electrons to fill

their outermost s and p orbitals.

All other atoms have to lose, gain or share

electrons to attain the stability

associated

with the noble gases.

slide3

Atoms which gain or lose electrons are called ions.

An ionic bond is the electrostatic attraction

that holds ions together.

A covalent bond is the sharing of electrons

between two atoms.

Atoms share electrons to attain

the electronic configuration and stability

of a noble gas.

Each atom has a tendency to form a certain number

of bonds in stable, neutral compounds.

bonding tendencies

Kernal

Skeleton

Bonds

diagram

diagram

H

H -

Li

1

Li

Li -

Be

2

Be

- Be -

B

3

B

- B -

Bonding Tendencies

H

1

bonding tendencies5

Kernal

Skeleton

Bonds

diagram

diagram

C

4

C

- C -

- N -

N

N

3

O

O

2

- O -

F

F

1

F -

Bonding Tendencies
skeleton diagrams
Skeleton Diagrams
  • These atoms are neutral in charge.
  • Only outer shell (valence) electrons are included.
  • Each atom tends to form a specific number of bonds when it forms a molecule.
  • Often, an unique atom is at the center of the structure.
skeleton diagrams of molecules

hydrogen

represents a single bond

H – F

fluoride

between two atoms

represents a double bond

=

carbon

O=C=O

(i.e., two bonds) between the

dioxide

same two atoms

º

represents a triple bond

boron

B º N

(i.e., three bonds) between

nitride

the same two atoms

beryllium

Be=O

Skeleton diagrams provide

some information about

the strength of the bond.

oxide

Skeleton Diagrams of Molecules

Skeleton diagrams indicate

which atoms are bound together.

skeleton diagrams of molecules8

H

methane

H

H

H

N

ammonia

H

H

C

H

H

H

C

H

H

O

O

formaldehyde

water

Skeleton Diagrams of Molecules

H-C-H bond angle

109.5°

H-N-H bond angle

107°

H-O-H bond angle

104.5°

H-C-H bond angle

~120°

Skeleton diagrams do not indicate bond angles!

skeleton diagrams of molecules9

fluorine

1

155 kJ·mol–1

F – F

gas

(difluorine)

oxygen

gas

O = O

2

495 kJ·mol–1

dioxygen)

(

nitrogen

N ºN

gas

3

941 kJ·mol–1

(dinitrogen)

Skeleton Diagrams of Molecules

Bond Order

Bond Energy

Which gas is the most reactive?

pairs activity
Pairs Activity
  • A pair of people will work on one problem:
  • One person is responsible for writing all the information.
  • The other person is responsible for saying what should be written.
on a card or a piece of paper
On a card or a piece of paper
  • Write each sequential step necessary to draw a skeleton diagram.
  • Number each step.
  • Amend and update the list.
    • Either person may do this.

Draw the skeleton diagram of acetic acid, CH3COOH

isomers
Isomers
  • An isomer is a compound with the same molecular formula, but different structure.
    • The atoms are linked differently together.

Draw the skeleton diagram of an isomer of

acetic acid, CH3COOH

isomers of c 2 h 4 o 2

H

H

H

H

C

C

O

H

H

C

C

O

H

O

O

H

H

H

H

C

O

C

H

O

Isomers of C2H4O2

glycolaldehyde

acetic acid

methyl formate

unstable isomers of c 2 h 4 o 2

H

H

H

O

C

C

C

H

O

C

C

C

H

H

C

C

O

C

O

O

O

O

H

C

O

O

H

H

H

H

C

C

H

O

O

Unstable Isomers of C2H4O2

Small ring structures

(containing 3 or 4 atoms

in the ring) are either

unstable or very reactive

sodium acetate
Sodium Acetate
  • Acetic acid reacts with sodium hydroxide to form sodium acetate and water.

Draw the skeleton diagram of sodium acetate.

draw the skeleton diagrams for
Draw the skeleton diagrams for
  • boric acid, H3BO3
  • aluminum hydroxide
h 3 bo 3 and al oh 3

H

O

H

H

O

B

O

H

O

H

H

O

Al

O

H3BO3 and Al(OH)3

Compare the Structures of Boric Acid

and Aluminum Hydroxide

aluminum hydroxide

boric acid

Both have similar

skeleton diagrams,

but different

chemical properties.

the periodic staircase separates metals and nonmetals
The Periodic StaircaseSeparates Metals and Nonmetals

Compare their position on the periodic table.

nonmetals

metals

Boron is a metalloid or semi-metal,

whereas aluminum is metallic.

compare the structures of boric acid and aluminum hydroxide

Which bond might break

to show each chemical character?

H

Metal oxides

are basic

O

H

H

O

B

O

H

H

O

Nonmetal oxides

are acidic

H

H

O

Al

O

H

O

Compare the Structures of Boric Acid and Aluminum Hydroxide

Both have amphoteric character.

skeleton diagrams20
Skeleton Diagrams
  • The skeleton bonding approach works for many molecules;
    • however, it fails to explain the bonding in some simple molecules and ions.
skeleton diagrams21
Skeleton Diagrams
  • What is the skeleton diagram for
    • carbon monoxide
    • ammonium ion
    • cyanide ion
  • Which atom(s) in each structure breaks the skeleton bonding rules?
skeleton diagram failures

or

O

O

C

C

+

+

H

H

or

H

H

H

H

N

N

H

H

or

N

C

N

C

Skeleton Diagram Failures
types of bonds formed

N

N

O

O

P

P

S

S

S

S

S

P

S

S

S

P

Types of Bonds Formed

Lighter members of a family

often form multiple bonds

Heavier members favor

additional single bonds.

heavier members of a family tend to form single bonds

O

O

Si

Si

O

O

C

O

O

carbon dioxide

Si

O

O

O

O

Si

Si

silicon dioxide

quartz, glass, sand

O

Heavier Members of a Familytend to form single bonds
bonding theories
Bonding Theories
  • Ionic Model
  • Skeleton Diagrams
    • Identifies how atoms are linked together
    • Fails to describe the bonding in ions and certain molecules (e.g., CO, NH4+, CN–)
    • Fails to explain the geometry of molecules