Chemistry bonding
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Chemistry: Bonding. Ionization Energy. Energy required to remove 1 mole of electrons from 1 mole of atoms. Nonmetals. Metals. Ionization Energy Trend. F. Nonmetals: gain e- have high Ionization Energies. Which element has the highest ionization energy?. Metals: lose e-

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Chemistry: Bonding

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Chemistry bonding

Chemistry: Bonding


Ionization energy

Ionization Energy

Energy required to remove 1 mole of electrons from 1 mole of atoms


Ionization energy trend

Nonmetals

Metals

Ionization Energy Trend

F

Nonmetals: gain e-

have high Ionization Energies

Which element has the highest ionization energy?

Metals: lose e-

have the lowest Ionization Energies


Electronegativity

Electronegativity

Measure of attraction of an atom for electrons

Atoms have equal electronegativity

This one has a higher electronegativity

This one has a MUCH higher

electronegativity


Electronegativity trend

F

Nonmetals

Metals

Fr

Electronegativity Trend

Fluorine has the greatest Electronegativity (attraction for electrons)

Francium has the lowest Electronegativity


Electronegativity practice

Electronegativity Practice

1) Draw in the bonding electrons

Example— H : F (bonding electrons closer to F)

Try these:Zn BrNa Cl

2) Arrange from lowest to highest electronegativities:

a) F(9), Sb(51), In(49), Se(34)

smallest largest

answer:

b) Ga (31), Fr(87), P(15), Ge(32), Zn(30)

smallest largest

answer:

:

:

InSbSeF

FrZnGaGeP


Chemistry bonding

Which has a greater electronegativity:

a metal or a non-metal?

Which is more electronegative:

Cu or S?

Br or Ga?


Polarity

Polarity

d

What is polarity?

Separation of charge

Symbol: d (Greek “delta”)

Meaning: “partial”

d + d-

Example: Cu : O

What causes polarity?

An unequal attraction toward the electrons


Polar molecules

Polar Molecules

  • Have distinguishable sides; or opposite ends

  • Can identify a top/bottom or right/left side

  • Asymmetrical


Nonpolar molecules

Nonpolar Molecules

  • Symmetrical

  • Equal distribution of charge

  • No d+ or d-

  • One side NOT distinguishable

  • Everything is the same around a central part


Chemical bonding

e -

e -

+

+

Chemical Bonding

  • Attraction between atoms

  • Electrostatic attraction (opposites attract) (+) to (-)

  • an atom’s protons are attracted to another atom’s electron


Bond types

Pauling Electronegativity Values

Bond Types

  • Determined by difference in electronegativity values—absolute value of DEN


Bond types1

Bond Types

  • Ionic

  • Covalent

  • Metallic


Ionic bonds

Cl

Cl

Na

+1

-1

Na

Ionic Bonds

Electrons are TRANSFERRED from a metal to a non-metal

electrostatic attraction


Ionic bonds d en 1 7

Pauling Electronegativity Values

Ionic Bonds: DEN > 1.7

DEN = 4.0 – 1.0 = 3.0

DEN = 3.5-1.0 = 2.5

Example: Sr – F

Example: Li—O

Acids, Bases, and Salts are Ionic compounds


Characteristics of ionic substances

Characteristics of Ionic Substances

  • VEEEERRRRRYYYY strong bonds

  • High melting points

  • Water soluble

  • Conduct electricity as liquids and in solution

  • Form defined crystals


Covalent bonds

Covalent Bonds

Formed by two or more atoms sharing an electron pair


Covalent bonds1

e -

e -

+

+

Covalent Bonds

Usually formed by two non-metals

(similar electronegativities)

Electrostatic attraction between atoms

A MOLECULE is two or more atoms covalently bonded


Covalent bonds d en 1 7

Covalent Bonds: DEN < 1.7

Si—C

DEN = 0.7

F—F

DEN = 0.0


Characteristics of covalent substances

Characteristics of Covalent Substances

Low melting points

Do not conduct electricity

Brittle


Types of covalent bonds

Types of Covalent Bonds

1. Non-polar Covalent

2. Polar Covalent


Types of covalent bonds1

Types of Covalent Bonds

1. Non-polar Covalent

equal sharing of e- pair

all diatomic molecules: Cl2, H2, Br2, I2

Why?

DEN = 0


Types of covalent bonds2

Types of Covalent Bonds

2. Polar Covalent

unequal sharing of e- pair

DEN : 0.3-1.7


Practice problems

Practice Problems

In H2S, which attracts electrons more?______

What is the approximate DEN? _____

S

0.3


Metallic bonds

Metallic Bonds

Characterized by free moving electrons

Found, obviously, in metals

Very strong bond


Summary

Summary

Identify the bond type in:

CaF2CuCl

polar-covalent

ionic


Lab 28 part 1 results

Lab 28 Part 1 Results

P

NP

P

NP

NP

P

P

NP

& P

NP

NP


Lab 28 part 2 results

Lab 28 Part 2 Results

P

NP

P

NP

BOTH

P

P

NP

BOTH

NP


Lewis dot diagrams

Lewis Dot Diagrams

Which electrons do dot diagrams symbolize?

outer electrons—valence electrons

(s and p orbitals)


Arsenic

H

H

H

H

Arsenic

Dot Diagram?

How many bonds can Arsenic form?

Dot Diagram for Hydrogen?

How many bonds can Hydrogen form?

3

1


Arsenic trihydride ash 3

As

H

H

H

Note: each “ “ is an electron pair

As

H

H

H

Arsenic Trihydride, AsH3

or


Oxygen

or

O

H

or

O

H

O

O

H

H

or

H

H

Oxygen

Dot Diagram?

How many bonds can Oxygen form?

Draw H2O

2


Boron

B

Boron

Dot Diagram?

How many bonds can Boron form?

Dot Diagram for Cl?

How many bonds can Cl form?

3

1


Boron trichloride bcl 3

Boron Trichloride, BCl3


Silicon

Si

I

Silicon

Dot Diagram?

How many bonds can Silicon form?

Dot Diagram for I?

How many bonds can I form?

4

1


Sii 4

I

I

Si

Si

I

I

I

I

I

I

SiI4


Bond angles bond length

Bond Angles & Bond Length

Bond Length

O

H

H

Bond Angle


Molecular shapes

Molecular Shapes

Pair Repulsion (VSEPR)

Stands for:

Valence Shell Electron Pair Repulsion

e- pairs repel each other and spread out as much as possible


Linear

Linear

2 outer electron pairs

Group IIA

Bond Angle = 180o

Ex: BeCl2


Linear double bonds

Linear—double bonds

Ex. CO2

In both, the shape is determined by electron repulsion


Trigonal planar

Trigonal Planar

3 outer electron pairs

Group III A

Bond Angle = 120o

Ex: BCl3


Trigonal planar double bonds

Trigonal Planar—double bonds

H2CO


Tetrahedron

Tetrahedron

4 outer e- pairs

Consider paired (bonding) e- pairs

&

unpaired e- pairs (“lonepairs”)


Perfect tetrahedron

Perfect Tetrahedron

ALL 4 e- pairs around central atom are bonded

Ex: CH4

Bond Angle = 109.5o


Pyramidal

..

Pyramidal

4 e- pairs—3 bonded and 1 lone pair

Ex: NH3

Bond Angle = 107o


Chemistry bonding

O

H

H

5

Bent

4 e- pairs —2 bonded and 2 lone pairs

Ex: H2O

Bond Angle = 104.5o


Chemistry bonding

Write dot diagrams for the following molecules:

Determine the molecular shape, bond angles, and polarity

 PBr3CH4

 H2OBeI2

AlCl3CO2

H2SSiF4


Pbr 3

P

Br

Br

Br

PBr3

d+

  • Pyramidal

  • 107o

  • polar

d-


H 2 o

O

H

H

H2O

  • Bent

  • 104.5o

  • Polar

d-

d+


Alcl 3

Cl

Al

Cl

Cl

AlCl3

  • Triganal planar

  • 120o

  • Non-polar


H 2 s

H2S

  • Bent

  • 104.5o

  • Polar

d-

d+


Ccl 4

CCl4

  • Perfect tetrahedron

  • 109.5o

  • Nonpolar


Chemistry bonding

CH4

  • Perfect tetrahedron

  • 109.5o

  • nonpolar


Bei 2

I

I

BeI2

  • Linear

  • 180o

  • Nonpolar


Chemistry bonding

CO2

  • Linear

  • 180o

  • Nonpolar


Sif 4

SiF4

  • Tetrahedron

  • 109.5o

  • Nonpolar


Asi 3

AsI3

  • Pyramidal

  • 107o

  • Polar


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