Bonding – Relationships between Microscopic Structure and Macroscopic Properties.

Bonding – Relationships Bonding – Relationships between Microscopic between Microscopic

Structure and Macroscopic Structure and Macroscopic PropertiesProperties

Chemical BondsChemical Bonds

Definition:Definition:

Any of several forces, especially ionic, metallic Any of several forces, especially ionic, metallic and covalent bonds, by which atoms or ions and covalent bonds, by which atoms or ions are bound in a molecule or crystal.are bound in a molecule or crystal.

Chemical Bond and Valence Chemical Bond and Valence Electron Electron

The electrons responsible for the chemical The electrons responsible for the chemical properties of atoms are those in the outer properties of atoms are those in the outer energy level: energy level: VALENCE ELECTRONS.VALENCE ELECTRONS.– Valence electrons - The electrons in the Valence electrons - The electrons in the

outer energy level.outer energy level.– Inner electrons -those in the energy levels Inner electrons -those in the energy levels

below. below.

Keeping Track of ElectronsKeeping Track of Electrons

Atoms in the same columnAtoms in the same columna. Have the same outer electron configuration.a. Have the same outer electron configuration.

b. Have the same valence electrons.b. Have the same valence electrons.

c. Easily found by looking up the group number c. Easily found by looking up the group number on the periodic table.on the periodic table.

d. Group 2A: Be, Mg, Ca, etc.d. Group 2A: Be, Mg, Ca, etc.

2 valence electrons2 valence electrons

Electron Dot Diagrams: Lewis Electron Dot Diagrams: Lewis StructuresStructures

1. A way of keeping track of 1. A way of keeping track of valence electrons.valence electrons.

2. How to write them2. How to write them3. Write the symbol.3. Write the symbol.4. Put one dot for each valence 4. Put one dot for each valence

electronelectron5. Don’t pair up until they have to5. Don’t pair up until they have to

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons.

First we write the symbol.

NThen add 1 electron at a time to each side.Until they are forced to pair up.

Write the electron dot diagram Write the electron dot diagram forfor

NaNa MgMg CC OO FF NeNe HeHe

Ionic CompoundsIonic Compounds- Ionic Bonds- Ionic Bonds

Electron Configurations for Electron Configurations for CationsCations

1. Metals lose electrons to attain noble gas 1. Metals lose electrons to attain noble gas configuration.configuration.

2. They make positive ions.2. They make positive ions.

3. If we look at electron configuration it makes 3. If we look at electron configuration it makes sense.sense.

Na 1sNa 1s222s2s222p2p663s3s11:: 1 valence electron 1 valence electron

NaNa++ 1s 1s222s2s222p2p6 6 :: noble gas configurationnoble gas configuration

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence electronsMetals will have few valence electrons

Ca

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence electronsMetals will have few valence electrons These will come offThese will come off

Ca

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence electronsMetals will have few valence electrons These will come offThese will come off Forming positive ionsForming positive ions

Ca+2

Write the electron Write the electron configuration diagram and configuration diagram and

orbital notation fororbital notation for NaNa MgMg CC OO FF NeNe HeHe

Electron Configurations for Electron Configurations for AnionsAnions

1. Nonmetals gain electrons to attain noble 1. Nonmetals gain electrons to attain noble gas configuration.gas configuration.

2. They make negative ions.2. They make negative ions.3. If we look at electron configuration it 3. If we look at electron configuration it

makes sense.makes sense. S 1sS 1s222s2s222p2p663s3s223p3p44: 6 valence electrons: 6 valence electrons SS-2-2 1s 1s222s2s222p2p663s3s223p3p66:: noble gas noble gas

configuration.configuration.

Electron Dots For AnionsElectron Dots For Anions

Nonmetals will have many Nonmetals will have many valence .electrons.valence .electrons.

They will gain electrons to fill outer shell.They will gain electrons to fill outer shell.

P P-3

Stable Electron ConfigurationStable Electron Configuration

1.All atoms react to achieve noble gas configuration.1.All atoms react to achieve noble gas configuration.

2.Noble gases have 2 s and 6 p electrons.2.Noble gases have 2 s and 6 p electrons.

3. 8 valence electrons .3. 8 valence electrons .

4. Also called the octet rule.4. Also called the octet rule.

Ar

Ionic BondingIonic Bonding

A. Anions and cations are held together by A. Anions and cations are held together by opposite charges.opposite charges.

B. Ionic compounds are called salts.B. Ionic compounds are called salts.

C. Simplest ratio is called the formula unit.C. Simplest ratio is called the formula unit.

D.The bond is formed through the transfer of D.The bond is formed through the transfer of electrons.electrons.

E. Electrons are transferred to achieve noble E. Electrons are transferred to achieve noble gas configuration.gas configuration.

Ionic BondingIonic Bonding

Na Cl

Ionic Bonding: Lewis StructureIonic Bonding: Lewis Structure

Na+ Cl -

Ionic BondingIonic Bonding

All the electrons must be accounted for!All the electrons must be accounted for!

Ca P

Ionic BondingIonic Bonding

Ca P

Ionic BondingIonic Bonding

Ca+2 P

Ionic Bonding

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca

Ionic Bonding

Ca+2 P-3

Ca P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2P

-3

Ca+2

Ionic Bonding

Ca3P2

Formula Unit

I. Properties of Ionic CompoundsI. Properties of Ionic Compounds

a. Crystalline structure.a. Crystalline structure.

b. A regular repeating arrangement of ions in b. A regular repeating arrangement of ions in the solid.the solid.

c. Structure is rigid.c. Structure is rigid.

Ionic CompoundsIonic Compounds

Ionic compounds Ionic compounds consist ofconsist of

a a latticelattice

of positiveof positive

and negative ions.and negative ions.

Lattice: three Lattice: three dimensional array of dimensional array of ions ions

NaCl:

Crystalline StructureCrystalline Structure

1. forms a lattice crystal- a 3-d geometric 1. forms a lattice crystal- a 3-d geometric structure.structure.

a. each negative ion is surrounded by a. each negative ion is surrounded by positive ions.positive ions.

b. Lattice energy- the energy b. Lattice energy- the energy required to break one mole of ionsrequired to break one mole of ions from the ionic bond. from the ionic bond.

i. the more – the harder it is to i. the more – the harder it is to

breakbreak

Ionic solids are brittleIonic solids are brittle

+ - + -+- +-

+ - + -+- +-

Ionic solids are brittleIonic solids are brittle

+ - + -

+- +-+ - + -

+- +-

Strong Repulsion breaks crystal apart.Strong Repulsion breaks crystal apart.

ConductivityConductivity

1.Conducting electricity is allowing charges to 1.Conducting electricity is allowing charges to move.move.

2.In a solid, the ions are locked in place.2.In a solid, the ions are locked in place.3. Ionic solids are insulators.3. Ionic solids are insulators.4. When melted, the ions can move around.4. When melted, the ions can move around.5. Melted ionic compounds conduct.5. Melted ionic compounds conduct.6. First get them to 800ºC.6. First get them to 800ºC.7. ELECTROLYTE-Dissolved in water they 7. ELECTROLYTE-Dissolved in water they

conduct.conduct.Salt water vs salt demo Salt water vs salt demo

Properties of Ionic CompoundsProperties of Ionic Compounds

Ions are strongly bonded- because of strong Ions are strongly bonded- because of strong forces between ions they haveforces between ions they have

High melting points.High melting points. High boiling points.High boiling points. High hardness scale.High hardness scale. Very rigid.Very rigid. Very brittle.Very brittle. Do not conduct electricity in solids. Only conduct Do not conduct electricity in solids. Only conduct

electricity in melts or aqueous (water) solutions.electricity in melts or aqueous (water) solutions. Do not conduct heat well.Do not conduct heat well.

MetalsMetals- Metallic Bonds- Metallic Bonds

Metallic BondsMetallic Bonds

How atoms are held together in the solid.How atoms are held together in the solid. Metals hold onto there valence electrons Metals hold onto there valence electrons

very weakly.very weakly. Think of them as positive ions floating in a Think of them as positive ions floating in a

sea of electrons.sea of electrons.

Sea of ElectronsSea of Electrons

+ + + ++ + + +

+ + + +

Electrons are free to move through the solid.Electrons are free to move through the solid. Metals conduct electricity.Metals conduct electricity.

MalleableMalleable

+ + + ++ + + +

+ + + +

Hammered into shape (bend).Hammered into shape (bend). Ductile - drawn into wires.Ductile - drawn into wires.

MalleableMalleable

+ + + +

+ + + ++ + + +

Electrons allow atoms to slide by.Electrons allow atoms to slide by.

Properties of MetalsProperties of Metals

Metals are strongly bonded- because of Metals are strongly bonded- because of strong forces between positive ions and the strong forces between positive ions and the “sea” of free electrons surrounding them.“sea” of free electrons surrounding them.

High melting points.High melting points. High boiling point.High boiling point. High hardness scale.High hardness scale. Malleable.Malleable. Ductile.Ductile. Conduct electricity.Conduct electricity. Conduct heat well.Conduct heat well.

Molecular CompoundsMolecular Compounds- Covalent Bonds- Covalent Bonds

Covalent BondsCovalent Bonds

How atoms are held together in molecular How atoms are held together in molecular compounds.compounds.

Nonmetal elements hold onto valence Nonmetal elements hold onto valence electrons tightly.electrons tightly.

All want to gain valence electrons to achieve All want to gain valence electrons to achieve octet or [He] configuration.octet or [He] configuration.

The lack of valence electron donor (e.g. The lack of valence electron donor (e.g. metals) results in the sharing of valence metals) results in the sharing of valence electrons.electrons.

Covalent Bonding

H Hand

Q: Who’s going to gain?

Who’s going to lose?

H HThey share

them!

H H Covalent Bond,

strong

Covalent Bonding

H HStrong interactions

within.

Weak interactions

between.

HH

HH

Properties of Molecular Properties of Molecular CompoundsCompounds

Molecules interact weakly due to lack of Molecules interact weakly due to lack of strong forces between them.strong forces between them.

Low melting points. Many molecular compounds Low melting points. Many molecular compounds are liquids at room temperature.are liquids at room temperature.

Low boiling points. Lots of molecular compounds Low boiling points. Lots of molecular compounds are gases at room temperature.are gases at room temperature.

Soft: very low hardness scale.Soft: very low hardness scale. Solids are brittle.Solids are brittle. Do not conduct electricity in solids nor in aqueous Do not conduct electricity in solids nor in aqueous

(water) solutions.(water) solutions. Do not conduct heat well.Do not conduct heat well.