IONIC BONDING

When an atom of a

nonmetal

takes one or more electrons from an atom of a

metal

so both atoms end up with eight valence electrons

IONIC BONDING

IS THE COMPOUND AN IONIC COMPOUND?

METAL NONMETAL SUBSCRIPTS

IONIC BONDING Metals will tend to lose electrons and become

POSITIVE CATIONS

Normal sodium atom loses one electron to become sodium ion

IONIC BONDING Nonmetals will tend to gain electrons and become

NEGATIVE ANIONS

Normal chlorine atom gains an electron to become a chloride ion

IONIC BONDING

SODIUM SULFATE

Crystalline structure

The

POSITIVE CATIONS

stick to the

NEGATIVE ANIONS

, like a magnet.

+ + + + + + + + +

COVALENT BONDING

When an atom of one

nonmetal shares nonmetal

one or more electrons with an atom of another so both atoms end up with eight valence electrons

COVALENT BONDING IS THE COMPOUND A COVALENT COMPOUND?

NONMETAL NONMETAL YES since it is made of only nonmetal elements

Covalent bonding • Fluorine has seven valence electrons F

Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven F F

l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons F F

l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons F F

l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons F F

l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons F F

l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons F F

l l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals F F

l l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals F F 8 Valence electrons

l l l l Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals 8 Valence electrons F F

Single Covalent Bond • A sharing of two valence electrons.

• Only nonmetals and Hydrogen.

• Different from an ionic bond because they actually form molecules.

• Two specific atoms are joined.

• In an ionic solid you can ’ t tell which atom the electrons moved from or to.

H Water Each hydrogen has 1 valence electron Each hydrogen wants 1 more O The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

Water • Put the pieces together • The first hydrogen is happy • The oxygen still wants one more H O

Water • The second hydrogen attaches • Every atom has full energy levels H O H

C O Carbon dioxide • Hybridization of Carbon! • CO 2 Carbon is central atom ( I have to tell you) • Carbon has 4 valence electrons • Wants 4 more • Oxygen has 6 valence electrons • Wants 2 more

Carbon dioxide • Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short C O

l Carbon dioxide Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

l Carbon dioxide The only solution is to share more O C O

l Carbon dioxide The only solution is to share more O C O

l Carbon dioxide The only solution is to share more O C O

l Carbon dioxide The only solution is to share more O C O

l Carbon dioxide The only solution is to share more O C O

l Carbon dioxide The only solution is to share more O C O

l l l Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in the bond O C O

l l l Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in the bond O 8 valence electrons C O

l l l Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in the bond 8 valence electrons O C O

l l l Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in the bond 8 valence electrons O C O

How to draw them 1. Add up all the valence electrons.

2. Count up the total number of electrons to give all atoms full outer shells.

3. Subtract #1 from #2.

4. Divide by 2 5. Tells you how many bonds - draw them.

6. Fill in the rest of the valence electrons to fill atoms up.

Examples • HCN C is central atom • N - has 5 valence electrons wants 8 • C - has 4 valence electrons wants 8 • H - has 1 valence electrons wants 2 • HCN has 5+4+1 = 10 • HCN wants 8+8+2 = 18 • (18-10)/2= 4 bonds • 3 atoms with 4 bonds -will require multiple bonds - not to H

HCN • Put in single bonds • Need 2 more bonds • Must go between C and N H C N

l l l l HCN Put in single bonds Need 2 more bonds Must go between C and N Uses 8 electrons - 2 more to add H C N

l l l l l 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 N to fill octet H C N

Polar Bonds • When the atoms in a bond are the same, the electrons are shared equally.

• This is a nonpolar covalent bond.

• When two different atoms are connected, the atoms may not be shared equally.

• This is a polar covalent bond.

• How do we measure how strong the atoms pull on electrons?

Electronegativity • A measure of how strongly the atoms attract electrons in a bond.

• The bigger the electronegativity difference the more polar the bond.

• 0.0 - 0.3 Covalent nonpolar • 0.3 - 1.67 Covalent polar • >1.67 Ionic

How to show a bond is polar • Isn ’ t a whole charge just a partial charge  d+ means a partially positive  d means a partially negative d+ H d Cl • The Cl pulls harder on the electrons • The electrons spend more time near the Cl

Polar Molecules Molecules with ends

Polar Molecules • Molecules with a positive and a negative end • Requires two things to be true ¬ The molecule must contain polar bonds This can be determined from differences in electronegativity.

Symmetry can not cancel out the effects of the polar bonds.

Must determine geometry first.

• HF • H 2 O • NH 3 • CCl 4 • CO 2 Is it polar?

Intermolecular Forces What holds molecules to each other

Intermolecular Forces • They are what make solid and liquid molecular compounds possible.

• The weakest are called van der Waal ’ s forces there are two kinds • Dispersion forces • Dipole Interactions – depend on the number of electrons – more electrons stronger forces – Bigger molecules

Dipole interactions • Depend on the number of electrons • More electrons stronger forces • Bigger molecules more electrons • Fluorine is a gas • Bromine is a liquid • Iodine is a solid

Dipole interactions • Occur when polar molecules are attracted to each other.

• Slightly stronger than dispersion forces.

• Opposites attract but not completely hooked like in ionic solids.

Dipole interactions • Occur when polar molecules are attracted to each other.

• Slightly stronger than dispersion forces.

• Opposites attract but not completely hooked d + H d F d + H d F

Dipole Interactions d + d d + d -

Hydrogen bonding • Are the attractive force caused by hydrogen bonded to F, O, or N.

• F, O, and N are very electronegative so it is a very strong dipole.

• The hydrogen partially share with the lone pair in the molecule next to it.

• The strongest of the intermolecular forces.

Hydrogen Bonding d + H O d H d +

Hydrogen bonding H O H

MOLECULAR SHAPES

OF COVALENT COMPOUNDS

VSepR tHEORY

What Vsepr means

Since electrons do not like each other, because of their negative charges, they orient themselves as far apart as possible, from each other.

This leads to molecules having specific shapes.

Things to remember

•

Atoms bond to form an Octet (

8 outer electrons/full outer energy level

)

•

Bonded electrons take up less space then un-bonded/unshared pairs of electrons.

Linear

EXAMPLE:

BeF

2

•

Number of Bonds = 2

•

Number of Shared Pairs of Electrons = 2

•

Bond Angle = 180

°

Trigonal Planar

EXAMPLE:

GaF

3

•

Number of Bonds = 3

•

Number of Shared Pairs of Electrons = 3

•

Number of Unshared Pairs of Electrons = 0

•

Bond Angle = 120

°

Bent #1

EXAMPLE:

H

2

O

•

Number of Bonds = 2

•

Number of Shared Pairs of Electrons = 2

•

Number of Unshared Pairs of Electrons = 2

•

Bond Angle = < 120

°

Bent #2

EXAMPLE:

O

3

•

Number of Bonds = 2

•

Number of Shared Pairs of Electrons = 2

•

Number of Unshared Pairs of Electrons = 1

•

Bond Angle = >120

°

Tetrahedral

EXAMPLE:

CH

4

•

Number of Bonds = 4

•

Number of Shared Pairs of Electrons = 4

•

Number of Unshared Pairs of Electrons = 0

•

Bond Angle = 109.5

°

Trigonal Pyramidal

EXAMPLE:

NH

3

•

Number of Bonds = 3

•

Number of Shared Pairs of Electrons = 4

•

Number of Unshared Pairs of Electrons = 1

•

Bond Angle = <109.5

°

Trigonal bIPyramidal

EXAMPLE:

NbF

5

•

Number of Bonds = 5

•

Number of Shared Pairs of Electrons = 5

•

Number of Unshared Pairs of Electrons = 0

•

Bond Angle = <120

°

OCTAHEDRAL

EXAMPLE:

SF

6

•

Number of Bonds = 6

•

Number of Shared Pairs of Electrons = 6

•

Number of Unshared Pairs of Electrons = 1

•

Bond Angle = 90

°

Metallic Bonds

•

How atoms are held together in the solid.

•

Metals hold onto there valence electrons very weakly .

•

Think of them as positive ions floating in a sea of electrons.

Sea of Electrons

•

Electrons are free to move through the solid.

•

Metals conduct electricity.

+ + + + + + + + + + + +

Metals are Malleable

•

Hammered into shape (bend).

•

Ductile - drawn into wires.

Malleable

+ + + + + + + + + + + +

Malleable

•

Electrons allow atoms to slide by.

+ + + + + + + + + + + +