Physical SciencePhysical Science

Ch. 19Ch. 19

Section 1Section 1

Stability in BondingStability in Bonding

• CompoundsCompounds–Two or more elements Two or more elements

combining to make a combining to make a substancesubstance

• Compounds have Compounds have different properties than different properties than the elements that make the elements that make them upthem up

• Chemical FormulaChemical Formula

–composed of symbols and composed of symbols and

subscripts indicating the subscripts indicating the

number of atoms of an number of atoms of an

element in a compound.element in a compound.

• SubscriptSubscript

–Means “written below”Means “written below”

• Atoms form compounds when Atoms form compounds when the compound is more stable the compound is more stable than the separate atoms.than the separate atoms.

• Noble gasesNoble gases–Elements in far right columnElements in far right column–Are more chemically stable than Are more chemically stable than

other elements because they other elements because they have a complete outer energy have a complete outer energy level.level.

• Stable CompoundsStable Compounds–Elements that do not have full Elements that do not have full

outer energy levels are more outer energy levels are more stable in compounds.stable in compounds.

–Atoms can Atoms can loselose, , gaingain, or , or shareshare electrons to get a stable electrons to get a stable outer energy level.outer energy level.

• Chemical bondChemical bond–the force that holds atoms the force that holds atoms

together in a compound.together in a compound.

Section 2Section 2

Types of BondsTypes of Bonds

Forming a bondForming a bond• Chemical BondsChemical Bonds

–When two elements come When two elements come together by either transferring together by either transferring or sharing electronsor sharing electrons

–When elements lose or gain When elements lose or gain electronselectrons

• The result of bonding is a The result of bonding is a net charge of net charge of zerozero

• IonIon–A charged particle because it has A charged particle because it has

more or fewer electrons than more or fewer electrons than protons.protons.

• CationCation–Positively charged ionPositively charged ion–When an atom loses an electronWhen an atom loses an electron

• AnionAnion–Negatively charged ionNegatively charged ion–When an atom gains an electronWhen an atom gains an electron

• MoleculesMolecules–Neutral particles formed as Neutral particles formed as

a result of sharing a result of sharing electrons.electrons.

• Covalent bondCovalent bond–the force of attraction the force of attraction

between atoms sharing between atoms sharing electrons.electrons.

• Ionic bondIonic bond–the force of attraction the force of attraction

between opposite charges between opposite charges of the ionsof the ions

• Chemical BondingChemical Bonding–Result is a neutral Result is a neutral

compound.compound.

–Sum of the charges is zero.Sum of the charges is zero.

• Atoms can form double or Atoms can form double or triple bonds depending on triple bonds depending on whether they share two or whether they share two or three pairs of electronsthree pairs of electrons–SaturatedSaturated

• all single bondsall single bonds

–UnsaturatedUnsaturated• Not all single bondsNot all single bonds• Must contain at least one Must contain at least one double or triple bonddouble or triple bond

• Polar moleculePolar molecule–Opposite ends have Opposite ends have opposite chargesopposite charges

• Nonpolar moleculeNonpolar molecule–electrons are shared electrons are shared equally.equally.

• Ionic CompoundsIonic Compounds–With ions (cations and anions)With ions (cations and anions)

–Between metal and non-metalBetween metal and non-metal

–Transfer of electronsTransfer of electrons

• Covalent CompoundsCovalent Compounds–With moleculesWith molecules

–Between two non-metalsBetween two non-metals

–Sharing of electronsSharing of electrons

Section 3Section 3

Writing Formulas and Writing Formulas and Naming CompoundsNaming Compounds

• Chemists use Chemists use symbolssymbols from the from the periodic table to write formulas periodic table to write formulas for compounds.for compounds.

• Binary compoundBinary compound–composed of two elementscomposed of two elements

• Oxidation numberOxidation number–how many electrons an atom has how many electrons an atom has

gained, lost, or shared to become gained, lost, or shared to become stablestable

–The apparent charge on an The apparent charge on an elementelement

• To write formulasTo write formulas–Use oxidation numbers Use oxidation numbers –Least common multiplesLeast common multiples

• When writing formulas, When writing formulas, remember that the compound is remember that the compound is neutral.neutral.

• A formula must have the correct A formula must have the correct number of positive and negative number of positive and negative ions so the charges balanceions so the charges balance–The formula must have a neutral The formula must have a neutral

chargecharge

Writing Binary CompoundsWriting Binary Compounds1.1. Write down first element & it’s Write down first element & it’s

oxidation numberoxidation number2.2. Write down second element & Write down second element &

it’s oxidation numberit’s oxidation number3.3. Add multiples of the Add multiples of the

appropriate element until total appropriate element until total charge is zerocharge is zero

4.4. Use subscripts to show ratio Use subscripts to show ratio of the atoms of each elementof the atoms of each element

Calcium OxideCalcium Oxide

Ca Ca +2+2

OO-2-2

+2 -2+2 -2

So 1 Ca and 1 OSo 1 Ca and 1 OCaOCaO

Lithium NitrideLithium NitrideLi Li +1+1

NN-3-3

+1 -3+1 -3+1 +1 +1+1

So 3 Li and 1 NSo 3 Li and 1 NLiLi33NN

Magnesium PhosphideMagnesium PhosphideMg Mg +2+2

PP-3-3

+2+2 -3-3+2+2

-3-3+2+2

So 3 Mg and 2 PSo 3 Mg and 2 PMgMg33PP22

Potassium SulfidePotassium SulfideK K +1+1

SS-2-2

+1+1 -2-2+1+1

So 2 K and 1 SSo 2 K and 1 S

KK22SS

Naming Binary CompoundsNaming Binary Compounds1.1. Write down name of Write down name of

first elementfirst element

2.2. Write down name of Write down name of second elementsecond element

3.3. Change the ending of Change the ending of the second element to the second element to –ide–ide

NaClNaCl

• SodiumSodium

ChlorineChlorine

-ide-ide

Sodium ChlorideSodium Chloride

KK22OO

• PotassiumPotassium

OxygenOxygen

-ide-ide

Potassium OxidePotassium Oxide

• PolyPoly–Means “many”Means “many”

• Polyatomic ionPolyatomic ion–positively or negatively positively or negatively charged, covalently charged, covalently bonded group of atomsbonded group of atoms

–Many atomsMany atoms

• HydrateHydrate–compound with water compound with water chemically attached to itchemically attached to it

• Binary covalent Binary covalent compoundscompounds–Name by using prefixes to Name by using prefixes to indicate how many atoms of indicate how many atoms of each element are in the each element are in the compoundcompound

Prefixes forPrefixes forCovalent Covalent

CompoundsCompounds

1.1. Mono-Mono-2.2. Di-Di-3.3. Tri-Tri-4.4. Tetra-Tetra-5.5. Penta-Penta-6.6. Hexa-Hexa-7.7. Hepta-Hepta-8.8. Octa-Octa-9.9. Non-Non-10.10. Dec-Dec-