covalentbonding.pptx

(1)

(2)

Bonds are…



Forces that hold groups of atoms

together and make them function

as a unit. Two types:

1)

Ionic bonds

–

transfer or

exchange

of electrons

(gained or lost; makes formula unit)

2)

Covalent bonds

–

sharing

of

electrons. The resulting

(3)

An ionic bond involves

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1. Sharing of

electrons

2. Exchange of

electrons

3. Sharing of metallic

bonds

4. Exchange of

(4)

In which type of bonds atoms share electrons?

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1. Covalent bonds 2. Metallic bonds 3. Ionic bonds

(5)

Molecules



Many

elements

found in nature

are in the form of

molecules

:

 _a_{neutral group of atoms}_joined

together by covalent bonds.



For example, air contains oxygen

molecules, consisting of two

oxygen atoms joined covalently

(6)

Covalent bonds



Nonmetals

_{hold on to their valence}

electrons.

 They can’t give away electrons to bond.

 But still want noble gas configuration.

 Get it by sharing valence electrons with each other = covalent bonding

 _{By sharing,}

both atoms

_{get to count} the electrons toward a noble gas

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Often atoms join so that each atom will have?

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1. An even number of

electrons.

2. Outermost energy level

that is full of electrons.

3. Equal number of protons

and electrons

4. More electrons that either

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Covalent Bonds are formed between?

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1. ions

2. Metal ions

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Covalent bonding

 Fluorine has seven valence

electrons (but would like to have 8)

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Covalent bonding

 Fluorine has seven valence

electrons

 A second atom also has seven

(11)

Covalent bonding

 Fluorine has seven valence

electrons

 A second atom also has seven

 By sharing electrons…

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Covalent bonding

electrons

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Covalent bonding

electrons

(14)

Covalent bonding

electrons

(15)

Covalent bonding

electrons

(16)

Covalent bonding

 Fluorine has seven valence electrons  A second atom also has seven



…

both end with full orbitals

(17)

Covalent bonding

 …both end with full orbitals

(18)

Covalent bonding

 …both end with full orbitals

F

(19)

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Molecular Compounds

 Compounds that are bonded

covalently (like in water, or carbon dioxide) are called molecular

compounds

 Molecular compounds tend to have

relatively lower melting and boiling

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Which of the following statements is

true concerning molecular compounds?

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1. They are composed

of one element

of ions

3. They are formed

from a metal and nonmetal.

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Molecular Compounds

 Thus, molecular compounds tend to

be

gases or liquids

at room temperature

_{Ionic compounds were solids}

 A molecular compound has a

molecular formula:

_{Shows how many atoms of each}

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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:

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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

(26)

Carbon dioxide

 Attaching 1 oxygen leaves the

oxygen 1 short, and the carbon 3 short

O

(27)

Carbon dioxide

 Attaching the second oxygen

leaves both of the oxygen 1 short, and the carbon 2 short

O

C

(28)

Carbon dioxide

 The only solution is to share more

O

C

(29)

Carbon dioxide

O

C

(30)

Carbon dioxide

O

C

(31)

Carbon dioxide

O

C

(32)

Carbon dioxide

O

C

(33)

Carbon dioxide

O

C

(34)

Carbon dioxide

 Requires two double bonds

 Each atom can count all the

electrons in the bond

O

C

(35)

Carbon dioxide

 The only solution is to share more  Requires two double bonds

 Each atom can count all the electrons in

the bond

O

C

O

(36)

Carbon dioxide

the bond

O

C

O

(37)

Carbon dioxide

the bond

O

C

O

(38)

Example

 NH₃, which is ammonia

 N – central atom; has 5

valence electrons, wants 8

 H - has 1 (x3) valence

electrons, wants 2 (x3)

 NH₃has 5+3 = 8

 NH₃wants 8+6 = 14

 (14-8)/2= 3 bonds

 4 atoms with 3 bonds

N

(39)

N H

H

Examples

 Draw in the bonds; start with singles

 All 8 electrons are accounted for

 Everything is full – done with this

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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

(41)

HCN

 Put single bond between each atom

 Need to add 2 more bonds

 Must go between C and N_{(Hydrogen is}

full)

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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

(43)

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