Warm-UpWarm-UpWhat are valence electrons?What are valence electrons?– Electrons in the highest occupied energy level of an Electrons in the highest occupied energy level of an

atom.atom.

Which group of atoms hardly react at all?Which group of atoms hardly react at all?– Nobel gases.Nobel gases.

Isotopes of an element have different number of Isotopes of an element have different number of A) neutronsA) neutrons C) protonsC) protons

B) electronsB) electrons D) nucleiD) nuclei

4-2: Ionic & Covalent Bonding4-2: Ionic & Covalent BondingDescribeDescribe how ionization energy affects how ionization energy affects ionic bonding.ionic bonding.

PredictPredict the composition of an ionic the composition of an ionic compound from its formula.compound from its formula.

DescribeDescribe how covalent bonds are formed. how covalent bonds are formed.

RelateRelate the properties of ionic and covalent the properties of ionic and covalent compounds.compounds.

Ionization EnergyIonization EnergyIt requires energy to remove an electron It requires energy to remove an electron from an atom.from an atom.

Energy has to be added to the electron to Energy has to be added to the electron to overcome its attraction to the nucleus.overcome its attraction to the nucleus.

This energy is called This energy is called ionization energyionization energy

High ionization energy = difficult to High ionization energy = difficult to remove.remove.

Low ionization energy = easy to remove.Low ionization energy = easy to remove.

Covalent BondsCovalent BondsIonic bonds are formed when electrons are Ionic bonds are formed when electrons are transferred between metals and transferred between metals and nonmetals.nonmetals.

Compounds exist with nonmetals only.Compounds exist with nonmetals only.

Nonmetals cannot transfer electrons to Nonmetals cannot transfer electrons to form a stable electron configuration.form a stable electron configuration.

Nonmetals share electrons.Nonmetals share electrons.

Sharing ElectronsSharing ElectronsAtoms that share electrons are called Atoms that share electrons are called molecules.molecules.

The atom can share multiple electrons to The atom can share multiple electrons to obtain a full outer shell of electrons.obtain a full outer shell of electrons.

Sharing ElectronsSharing ElectronsMolecules are neutral groups of atoms that Molecules are neutral groups of atoms that are joined by one or more covalent bond.are joined by one or more covalent bond.

Covalent bonds are formed with non-Covalent bonds are formed with non-metals only. metals only.

Nonmetals that bond with themselves are Nonmetals that bond with themselves are called diatomic molecules.called diatomic molecules.

HH22, N, N22, O, O22, F, F22, Cl, Cl22, Br, Br22, I, I22,,

Multiple Covalent BondingMultiple Covalent BondingAtoms can share multiple pairs of Atoms can share multiple pairs of electronselectrons

Types of covalent bondsTypes of covalent bonds– Single – one shared set of electronsSingle – one shared set of electrons– Double – two shared sets of electronsDouble – two shared sets of electrons– Triple – three shared sets of electronsTriple – three shared sets of electrons– Quadruple can not form because of electron Quadruple can not form because of electron

repulsion.repulsion.

Ionic compound StructureIonic compound StructureAll ionic compound form crystals.All ionic compound form crystals.

The formula does not tell how the ions are The formula does not tell how the ions are arranged in the compound.arranged in the compound.

Looking at samples help to identify the Looking at samples help to identify the pattern.pattern.

Ionic compound form a Ionic compound form a crystal latticecrystal lattice– A repeating pattern of ions.A repeating pattern of ions.

Properties of CompoundsProperties of CompoundsIonic CompoundsIonic Compounds– High melting pointHigh melting point– Poor electrical conductor in solid state.Poor electrical conductor in solid state.– Good electrical conductor in liquid state.Good electrical conductor in liquid state.– Tend to shatter when struck.Tend to shatter when struck.– Generally good dissolving in water.Generally good dissolving in water.

Properties of CompoundsProperties of CompoundsCovalent CompoundsCovalent Compounds– Low melting pointsLow melting points– Generally soft and pliable (won’t shatter).Generally soft and pliable (won’t shatter).– Poor conductors of heat and electricity.Poor conductors of heat and electricity.– Most covalent compounds are poorly soluble Most covalent compounds are poorly soluble

in water.in water.

SummarySummaryWhich type of elements make covalent Which type of elements make covalent bonds?bonds?– Nonmetals.Nonmetals.

Which type of bond is stronger? Ionic or Which type of bond is stronger? Ionic or covalentcovalent– Ionic because ionic compounds have very Ionic because ionic compounds have very

high melting points.high melting points.

Which type of compound does not usually Which type of compound does not usually dissolve in water?dissolve in water?– CovalentCovalent