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Chapter 4 The Structure of Matter How atoms form compounds.
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Transcript of Chapter 4 The Structure of Matter How atoms form compounds.
Chapter 4Chapter 4
The Structure of MatterThe Structure of Matter
How atoms form compoundsHow atoms form compounds
CompoundsCompounds Formed when two or more Formed when two or more
elements combineelements combine Must make a chemical changeMust make a chemical change New propertiesNew properties Atoms from the different elements Atoms from the different elements
form bondsform bonds Chemical Bond-Chemical Bond- the attractive the attractive
force that holds different atoms or force that holds different atoms or ions togetherions together
CompoundsCompounds Every compound has a specific Every compound has a specific
ratio of atomsratio of atoms Written as a chemical formulaWritten as a chemical formula HH22O, CO, C1212HH2222OO1212, NaCl, NaCl The ratio is the same every time, The ratio is the same every time,
every whereevery where Different ratio means a different Different ratio means a different
compoundcompound
Chemical StructureChemical Structure Shows how the atoms are Shows how the atoms are
arranged in the compoundarranged in the compound How the atoms or ions are How the atoms or ions are
connectedconnected In order to specify where we needIn order to specify where we need– Bond lengthBond length- distance between - distance between
the nucleithe nuclei– Bond angleBond angle- Angle between - Angle between
atoms (requires two bonds)atoms (requires two bonds)
ModelsModels Ball and stick- Ball represents Ball and stick- Ball represents
atoms, stick represents bondsatoms, stick represents bonds Easy to see bond anglesEasy to see bond angles Structural formulas- drawn with Structural formulas- drawn with
connections between atoms shown.connections between atoms shown.
HO
H
H
H
H
C O H
ModelsModels Space-filling – Shows that atoms Space-filling – Shows that atoms
the right size and in the right the right size and in the right place.place.
CC44HH99OO22NN
2 Types of structures2 Types of structures NetworksNetworks A large number of atoms, all A large number of atoms, all
bonded togetherbonded together Atoms bondedAtoms bonded Or ions opposite chargesOr ions opposite charges
Network SolidsNetwork Solids Many atoms all bonded togetherMany atoms all bonded together Quartz is SiOQuartz is SiO2 2
Major component of rocks.Major component of rocks. Each Silicon bonded to 4 oxygen atomsEach Silicon bonded to 4 oxygen atoms Angle is 109.5ºAngle is 109.5º Gives it a strong rigid Gives it a strong rigid
structurestructure Makes rocks hard.Makes rocks hard. Gives them a highGives them a high
melting and boiling pointmelting and boiling point
Network SolidsNetwork Solids Ions bond togetherIons bond together Opposite charges attractOpposite charges attract All the positives getAll the positives get
surrounded by negatives surrounded by negatives Get a repeatingGet a repeating
pattern pattern RigidRigid BrittleBrittle High mp and bpHigh mp and bp
MoleculesMolecules Specific atoms joined togetherSpecific atoms joined together Weaker attractions than ions.Weaker attractions than ions. Low melting and boiling pointsLow melting and boiling points Things we know as gases and Things we know as gases and
liquidsliquids Stronger attraction- higher melting Stronger attraction- higher melting
and boiling temperaturesand boiling temperatures
BondingBonding When the valence electrons When the valence electrons
interactinteract Atoms react to achieve full Atoms react to achieve full
outermost energy levelsoutermost energy levels Two ways to do thisTwo ways to do this– Share electronsShare electrons– Transfer electronsTransfer electrons
Keeping Track of ElectronsKeeping Track of Electrons Atoms in the same columnAtoms in the same column Have the same outer electron Have the same outer electron
configuration.configuration. Have the same valence electrons.Have the same valence electrons. Group 1 has 1 valence electronsGroup 1 has 1 valence electrons Group 2 has 2 valence electronsGroup 2 has 2 valence electrons Group 13 has 3 valence electronsGroup 13 has 3 valence electrons Group 14 has 4 valence electronsGroup 14 has 4 valence electrons etcetc
1 23 4 5 6 7
8Helium only has 2 valence electrons
Electron Dot diagramsElectron Dot diagrams A way of keeping track A way of keeping track
of valence electrons.of valence electrons. How to write themHow to write them Write the symbol.Write the symbol. Put one dot for each Put one dot for each
valence electronvalence electron Don’t pair up until Don’t pair up until
they have tothey 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
Electron Configurations for Electron Configurations for CationsCations
Metals lose electrons to fill their Metals lose electrons to fill their outer levelsouter levels
They make positive ions.They make positive ions.
Electron Dots For CationsElectron Dots For Cations
Metals will have few valence Metals will have few valence electronselectrons
Ca
Electron Dots For CationsElectron Dots For Cations
Metals will have few valence Metals will have few valence electronselectrons
These will come offThese will come off
Ca
Electron Dots For CationsElectron Dots For Cations
Ca+2
Metals will have few valence Metals will have few valence electronselectronsThese will come offThese will come offForming positive ionsForming positive ions
Electron Configurations for Electron Configurations for AnionsAnions
Nonmetals gain electrons to fill their Nonmetals gain electrons to fill their outer levelsouter levels
They make negative ions.They make negative ions.
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 ArrangementsStable Arrangements All atoms react to fill their outer All atoms react to fill their outer
levelslevels Noble gases have full outer energy Noble gases have full outer energy
levels.levels. 8 valence electrons .8 valence electrons . Also called the octet rule.Also called the octet rule.
Ar
Ionic BondingIonic Bonding Anions and cations are held Anions and cations are held
together by opposite charges.together by opposite charges. The bond is formed through the The bond is formed through the
transfer of electrons.transfer of electrons. Electrons are transferred to fill Electrons are transferred to fill
their outer levelstheir outer levels
Ionic BondingIonic Bonding
Na Cl
Ionic BondingIonic Bonding
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
Properties of Ionic CompoundsProperties of Ionic Compounds Crystalline structure.Crystalline structure. A regular repeating arrangement A regular repeating arrangement
of ions in the solid.of ions in the solid. Ions are strongly bonded.Ions are strongly bonded. Structure is rigid.Structure is rigid. High melting points- because of High melting points- because of
strong forces between ions.strong forces between ions.
Crystalline structureCrystalline structure
Do they Conduct?Do they Conduct? Conducting electricity is allowing Conducting electricity is allowing
charges to move.charges to move. In a solid, the ions are locked in place.In a solid, the ions are locked in place. Ionic solids are insulators.Ionic solids are insulators. When melted, the ions can move When melted, the ions can move
around.around. Melted ionic compounds conduct.Melted ionic compounds conduct. First get them to 800ºC.First get them to 800ºC. Dissolved in water they conduct.Dissolved in water they conduct.
Metallic BondsMetallic Bonds How atoms are held together in How atoms are held together in
the solid metalthe solid metal Metals hold onto there valence Metals hold onto there valence
electrons very weakly.electrons very weakly. Think of them as positive ions Think of them as positive ions
floating in a sea of electrons.floating in a sea of electrons.
Sea of ElectronsSea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through Electrons are free to move through the solid.the solid.
Metals conduct electricity.Metals conduct electricity.
Metals are MalleableMetals are Malleable Hammered into shape (bend).Hammered into shape (bend). Ductile - drawn into wires.Ductile - drawn into wires.
MalleableMalleable
+ + + ++ + + +
+ + + +
MalleableMalleable
+ + + +
+ + + ++ + + +
Electrons allow atoms to slide by.Electrons allow atoms to slide by.
Ionic solids are brittleIonic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittleIonic solids are brittle
+ - + -
+- +-+ - + -
+- +-
Strong Repulsion breaks crystal Strong Repulsion breaks crystal apart.apart.
Covalent bondsCovalent bonds Nonmetals hold onto their valence Nonmetals hold onto their valence
electrons.electrons. They can’t give away electrons to They can’t give away electrons to
bond.bond. Still want full outer levelStill want full outer level Get it by sharing valence electrons Get it by sharing valence electrons
with each other.with each other. By sharing both atoms get to count By sharing both atoms get to count
the electrons toward noble gas the electrons toward noble gas configuration.configuration.
Covalent bondingCovalent bonding Fluorine has seven valence Fluorine has seven valence
electronselectrons
F
Covalent bondingCovalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has seven
Covalent bondingCovalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons
Covalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons
Covalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons
Covalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons
Covalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons
Covalent bonding
F F
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level
Covalent bonding
F F8 Valence electrons
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level
Covalent bonding
F F8 Valence electrons
Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level
Single Covalent BondSingle Covalent Bond A sharing of two valence electrons.A sharing of two valence electrons. Only nonmetals and Only nonmetals and Hydrogen.Hydrogen. Different from an ionic bond Different from an ionic bond
because they actually form because they actually form molecules.molecules.
Two specific atoms are joined.Two specific atoms are joined. In an ionic solid you can’t tell In an ionic solid you can’t tell
which atom the electrons moved which atom the electrons moved from or to.from or to.
How to show how they formedHow to show how they formed It’s like a jigsaw puzzle.It’s like a jigsaw puzzle. I have to tell you what the final I have to tell you what the final
formula is.formula is. You put the pieces together to end You put the pieces together to end
up with the right formula.up with the right formula. For example- show how water is For example- show how water is
formed with covalent bonds.formed with covalent bonds.
WaterWater
H
O
Each hydrogen has 1 Each hydrogen has 1 valence electronvalence electron
Each hydrogen wants 1 Each hydrogen wants 1 moremore
The oxygen has 6 valence The oxygen has 6 valence electronselectrons
The oxygen wants 2 moreThe oxygen wants 2 more
They share to make each They share to make each other happyother happy
WaterWater Put the pieces togetherPut the pieces together The first hydrogen is happyThe first hydrogen is happy The oxygen still wants one moreThe oxygen still wants one more
H O
WaterWater The second hydrogen attachesThe second hydrogen attaches Every atom has full energy levelsEvery atom has full energy levels
H OH
Multiple BondsMultiple Bonds Sometimes atoms share more than Sometimes atoms share more than
one pair of valence electrons.one pair of valence electrons. A double bond is when atoms A double bond is when atoms
share two pair (4) of electrons.share two pair (4) of electrons. A triple bond is when atoms share A triple bond is when atoms share
three pair (6) of electrons.three pair (6) of electrons.
Carbon dioxideCarbon dioxide COCO22 - - Carbon is central Carbon is central
atomatom ( I have to tell you)( I have to tell you)
Carbon has 4 valence Carbon has 4 valence electronselectrons
Wants 4 moreWants 4 more Oxygen has 6 valence Oxygen has 6 valence
electronselectrons Wants 2 moreWants 2 more
O
C
Carbon dioxideCarbon dioxide Attaching 1 oxygen leaves the Attaching 1 oxygen leaves the
oxygen 1 short and the carbon 3 oxygen 1 short and the carbon 3 shortshort
OC
Carbon dioxide Attaching the second oxygen leaves
both oxygen 1 short and the carbon 2 short
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more
OCO
Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in
the bond
OCO
Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in
the bond
OCO8 valence electrons
Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in
the bond
OCO8 valence electrons
Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in
the bond
OCO
8 valence electrons
Another way of indicating Another way of indicating bondsbonds
Often use a line to indicate a bondOften use a line to indicate a bond Called a structural formulaCalled a structural formula Each line is 2 valence electronsEach line is 2 valence electrons
H HO =H HO
Structural ExamplesStructural Examples
H C N
C OH
H
C has 8 C has 8 electrons electrons because each because each line is 2 line is 2 electronselectrons
Ditto for NDitto for N
Ditto for C hereDitto for C here Ditto for ODitto for O