Bonds Bonds Chemical BondsChemical Bonds

Unit 3Unit 3 Chemistry Chemistry II

Elements and Elements and Periodic TablePeriodic Table

Elements are organized into Elements are organized into columns and rowscolumns and rows Columns have same number of Columns have same number of

valence electrons (generally)valence electrons (generally) Rows for s and p are in the same Rows for s and p are in the same

energy levelenergy level Metals on left, nonmetals on right, Metals on left, nonmetals on right,

metalloids are stair-step in p block. metalloids are stair-step in p block. These divide metals and nonmetalsThese divide metals and nonmetals

Element Element ClassificationClassification

MetalsMetals Solids at room temperatureSolids at room temperature Malleable and ductileMalleable and ductile Good conductorsGood conductors

NonmetalsNonmetals Gases at room temperature (bromine is Gases at room temperature (bromine is

exception)exception) Brittle and dullBrittle and dull Poor conductorsPoor conductors

MetalloidsMetalloids Physical and chemical properties of metals Physical and chemical properties of metals

and nonmetalsand nonmetals

Nuclear AttractionNuclear Attraction

Shielding electronsShielding electrons Electrons in the inner energy levels Electrons in the inner energy levels

block the attraction from the block the attraction from the nucleus to electrons in the outer nucleus to electrons in the outer energy levelenergy level

Effective nuclear chargeEffective nuclear charge Attraction between the nucleus and Attraction between the nucleus and

the electrons in the outer energy the electrons in the outer energy levellevel

Periodic TrendsPeriodic Trends

Atomic radiusAtomic radius

ElectronegativityElectronegativity

Ionization energyIonization energy

Ionic radiusIonic radius

BondingBonding

Chemical BondingChemical Bonding Bond is a force holding two Bond is a force holding two

atoms togetheratoms together Type of bond is determined Type of bond is determined

by the number of valence by the number of valence electronselectrons

IonsIons IonsIons

Charged particles from gaining or losing Charged particles from gaining or losing electronselectrons

Done to reach a noble gas configuration (to Done to reach a noble gas configuration (to be stable)be stable)

Number of electrons gained/lost depends on Number of electrons gained/lost depends on the number of valence electronsthe number of valence electrons

Positive ions (cations) - metalsPositive ions (cations) - metals Atom loses one or more electronsAtom loses one or more electrons Transition metals can form more than one Transition metals can form more than one

type of cationtype of cation Negative ions (anions) - nonmetalsNegative ions (anions) - nonmetals

Atom gains one or more electronsAtom gains one or more electrons

Naming IonsNaming Ions

Cations keep their name Cations keep their name and add the word ionand add the word ion

Anions change the suffix to Anions change the suffix to --- -ide and add the word --- -ide and add the word ion(oxide ion, chloride ion)ion(oxide ion, chloride ion)

Ionic BondsIonic Bonds

Result from:Result from: Metal cation losing one or more electronsMetal cation losing one or more electrons

Nonmetal anion gaining one or more Nonmetal anion gaining one or more electronselectrons

Opposite charges attracting one anotherOpposite charges attracting one another

NamingNaming Cation is listed first (keeps its name)Cation is listed first (keeps its name)

Anion is listed second (has –ide suffix)Anion is listed second (has –ide suffix)

Polyatomic IonsPolyatomic Ions

Ions made from more than one Ions made from more than one atomatom

Charge relates to the entire Charge relates to the entire group of atomsgroup of atoms Indicates the number of Indicates the number of

electrons needed to gain or electrons needed to gain or lose lose

List found on page 224List found on page 224..

Ionic Bonds and Ionic Bonds and MetalsMetals

S Block metals have one S Block metals have one oxidation number (number of oxidation number (number of electrons can lose)electrons can lose)

D and P block metals can have D and P block metals can have more than one oxidation statemore than one oxidation state Must indicate the number of Must indicate the number of

electrons lost with a Roman electrons lost with a Roman numeral in the namenumeral in the name

Transition Metal Transition Metal ExamplesExamples

Copper (II) chlorideCopper (II) chloride

Silver (I) sulfideSilver (I) sulfide

Lead (IV) oxideLead (IV) oxide

Chromium (III) bromideChromium (III) bromide

Vanadium (V) selenideVanadium (V) selenide

Metallic BondsMetallic Bonds

Metals can exist bonded to other metal Metals can exist bonded to other metal atomsatoms

Sea of Electrons model proposes electrons Sea of Electrons model proposes electrons travel through the metal atomstravel through the metal atoms Electrons changing atoms are called Electrons changing atoms are called

delocalizeddelocalized Metallic properties are because of delocalized Metallic properties are because of delocalized

electrons (high MP/BP, good conductor, electrons (high MP/BP, good conductor, malleable)malleable)

Alloys are combinations of different metalsAlloys are combinations of different metals

Covalent BondsCovalent Bonds

Occur to achieve a noble gas Occur to achieve a noble gas configuration (8 valence electrons)configuration (8 valence electrons)

Electrons are shared between two Electrons are shared between two nonmetalsnonmetals

More common than ionic bonds (NMore common than ionic bonds (N22, , HH22O, COO, CO22))

Types of Covalent Types of Covalent BondsBonds

Single covalent bonds share one pair Single covalent bonds share one pair of electrons (one electron from each of electrons (one electron from each atom)atom)

Double covalent bonds share two Double covalent bonds share two pairs of electrons pairs of electrons

Triple covalent bonds share three Triple covalent bonds share three pairs of electrons pairs of electrons

Bond StrengthBond Strength

The longer the covalent bond, The longer the covalent bond, the weaker the bond is the weaker the bond is

The shorter the covalent bond, The shorter the covalent bond, the stronger the bond isthe stronger the bond is

Triple bonds are the strongest; Triple bonds are the strongest; single bonds are the weakestsingle bonds are the weakest

Covalent NamingCovalent Naming

Binary covalent moleculesBinary covalent molecules

First elementFirst element Keeps its nameKeeps its name Uses a prefix except if only one Uses a prefix except if only one

atomatom

Second elementSecond element Suffix is –ideSuffix is –ide ALWAYS uses a prefixALWAYS uses a prefix

Lewis StructuresLewis Structures Method used to predict the shape of Method used to predict the shape of

moleculesmolecules

Dots represent valence electrons and a Dots represent valence electrons and a dash/line represent a covalent bonddash/line represent a covalent bond

Hydrogen is always an end atomHydrogen is always an end atom

Atom with least attraction for shared Atom with least attraction for shared electrons is often the central atom electrons is often the central atom (Usually furthest left)(Usually furthest left)

Start on left of formula and work to rightStart on left of formula and work to right

VSEPR ModelVSEPR Model

Molecular shape can be determined based Molecular shape can be determined based the Lewis structure of a moleculethe Lewis structure of a molecule

Shape will determine many of the physical Shape will determine many of the physical and chemical characteristics of a moleculeand chemical characteristics of a molecule

VSEPR (Valence Shell Electron Pair VSEPR (Valence Shell Electron Pair Repulsion) is the modelRepulsion) is the model Arrangement is based on minimizing Arrangement is based on minimizing

repulsion around a central atomrepulsion around a central atom Lone pairs repel more than bonded pairsLone pairs repel more than bonded pairs Different shapes have different Different shapes have different

angles/propertiesangles/properties See page 260 See page 260

Electronegativity and Electronegativity and PolarityPolarity

Types of bonds are determined through difference Types of bonds are determined through difference in electronegativity (EN)in electronegativity (EN)

Difference in EN greater than 1.7 is an ionic bondDifference in EN greater than 1.7 is an ionic bond

Difference in EN between 0.3 and 1.7 is a polar Difference in EN between 0.3 and 1.7 is a polar covalent bondcovalent bond Electrons tend to be in the orbital of the element with Electrons tend to be in the orbital of the element with

higher electronegativity (partial negative)higher electronegativity (partial negative)

Difference in EN less than 0.3 is a nonpolar Difference in EN less than 0.3 is a nonpolar covalent bondcovalent bond Electrons are shared evenly (no partial charges)Electrons are shared evenly (no partial charges)

PolarityPolarity

Bonds vs. MoleculesBonds vs. Molecules

Bonds are based on electronegativity Bonds are based on electronegativity differencesdifferences

Molecules have polarity based on Molecules have polarity based on geometrygeometry All polar bonds can be nonpolar moleculeAll polar bonds can be nonpolar molecule

Intermolecular Intermolecular Forces (IMF)Forces (IMF)

Attraction between two moleculesAttraction between two molecules

Strength of IMF helps determine the phase of matter of a Strength of IMF helps determine the phase of matter of a substancesubstance

London dispersion forces (dispersion forces)London dispersion forces (dispersion forces) Between nonpolar moleculesBetween nonpolar molecules Weakest of IMFs Weakest of IMFs

Dipole – dipole forcesDipole – dipole forces Between polar moleculesBetween polar molecules 1% as strong as a covalent bond1% as strong as a covalent bond

Hydrogen bonding (strongest IMF)Hydrogen bonding (strongest IMF) Specific dipole-dipole force between H and N, O, or FSpecific dipole-dipole force between H and N, O, or F

Properties of Ionic Properties of Ionic CompoundsCompounds

Ionic compounds form a crystal latticeIonic compounds form a crystal lattice Crystal lattice is a highly ordered three Crystal lattice is a highly ordered three

dimensional shapedimensional shape

Positive ions are surrounded by negative Positive ions are surrounded by negative ions and negative ions are surrounded by ions and negative ions are surrounded by positive ionspositive ions

Lattice energy is the energy needed to Lattice energy is the energy needed to separate one mole of ions separate one mole of ions The more negative the lattice energy, the The more negative the lattice energy, the

stronger the attractionstronger the attraction

Values are negative because energy is Values are negative because energy is released when broken (exothermic)released when broken (exothermic)

Properties of Ionic Properties of Ionic CompoundsCompounds

Due to strong attractions between positive Due to strong attractions between positive and negative ionsand negative ions High melting points and boiling pointsHigh melting points and boiling points

Can conduct electricity in a liquid state (or Can conduct electricity in a liquid state (or aqueous state)aqueous state)

Hard and brittleHard and brittle

Properties of Properties of Covalent MoleculesCovalent Molecules

Crystal lattice structure with complete Crystal lattice structure with complete molecules at the pointsmolecules at the points

Low melting points and boiling pointsLow melting points and boiling points

Can be hard/soft, flexibleCan be hard/soft, flexible

Nonpolar molecules will not conduct Nonpolar molecules will not conduct electricityelectricity