Chapter 22: Chapter 22: Chemical BondingChemical Bonding

Section 1– Section 1– Electrons and Electrons and

Chemical BondingChemical BondingChemical bonding – joining of atoms to Chemical bonding – joining of atoms to form new substancesform new substances

Chemical bond – interaction that holds Chemical bond – interaction that holds 2 atoms together2 atoms together

Valence ElectronsValence Electronsee-- in outermost shell in outermost shell

Determines an atomDetermines an atom’’s chemical s chemical propertiesproperties

Used to form bondsUsed to form bonds

Within a group, or family, atoms have Within a group, or family, atoms have the same # of valence ethe same # of valence e--

Atoms with fewer than 8 valence eAtoms with fewer than 8 valence e- - are are more likely to form bonds than an atom more likely to form bonds than an atom with 8 ewith 8 e- -

Types of BondsTypes of BondsIonic, Covalent, MetallicIonic, Covalent, Metallic

Atoms bond by sharing, gaining or losing eAtoms bond by sharing, gaining or losing e-- to have a filled outermost energy level.to have a filled outermost energy level.

A full set = 2 eA full set = 2 e-- for a few of the elements for a few of the elements

A full set = 8 eA full set = 8 e-- for most elements for most elements

Which ones? Why?Which ones? Why?

Section 2: Section 2: Ionic BondsIonic Bonds

Bonds form by Bonds form by gaining or losing gaining or losing ee--, resulting in , resulting in charged atoms charged atoms called ions. called ions.

Oppositely charged Oppositely charged ions are attracted ions are attracted to one anotherto one another

Metal + NonmetalMetal + Nonmetal

Positive and Positive and negative charges negative charges cancel each other cancel each other out to form an out to form an overall neutral overall neutral compoundcompound

Metal AtomsMetal AtomsHave few valence electrons Have few valence electrons

Usually lose these valence eUsually lose these valence e-- and form and form positive ions (cations)positive ions (cations)

Some transition metal ions can have multiple Some transition metal ions can have multiple charges. For example, iron can have a +2 or a charges. For example, iron can have a +2 or a +3 charge.+3 charge.

The charge is written as a superscript of the The charge is written as a superscript of the symbol:symbol:

Ex. KEx. K++, Ca, Ca2+2+, Al, Al3+3+

Nonmetal atomsNonmetal atomsHave almost full valence shellsHave almost full valence shells

Tend to gain eTend to gain e-- from other atoms and from other atoms and form negative ions (anions)form negative ions (anions)

The charge is written as a superscript The charge is written as a superscript of the formula:of the formula:

Ex. PEx. P3-3-, S, S2-2-, Cl, Cl--

Polyatomic IonsPolyatomic IonsPoly = Poly = ““manymany””

Polyatomic = Polyatomic = ““many atomsmany atoms””

A group of atoms that behave as a A group of atoms that behave as a single ion with an overall positive or single ion with an overall positive or negative chargenegative charge

Treat the polyatomic ion as a Treat the polyatomic ion as a single single unit with a single charge. unit with a single charge.

Writing formulas Writing formulas for ionic for ionic compoundscompoundsThe number of positive charges and The number of positive charges and

negative charges must negative charges must balancebalance in an in an ionic compoundionic compound

The formula represents this balanceThe formula represents this balance

Subscripts are used to indicate the Subscripts are used to indicate the ratio of elements in the compound (no ratio of elements in the compound (no ““11””))

Writing formulas Writing formulas for ionic for ionic compoundscompounds1.1. Find oxidation number (charge) for Find oxidation number (charge) for

both partsboth partsa.a. For elements in groups 1 and 2, use For elements in groups 1 and 2, use

group #. Boron family is 3+, Carbon group #. Boron family is 3+, Carbon family ± 4, Nitrogen family is -3, family ± 4, Nitrogen family is -3, Oxygen family is -2 and halogens are -1.Oxygen family is -2 and halogens are -1.

b.b. For cations followed by a roman numeral, For cations followed by a roman numeral, the roman numeral the roman numeral isis the oxidation # the oxidation #

c.c. For polyatomic ions check the list. For polyatomic ions check the list. Do Do not not change the subscripts within the change the subscripts within the polyatomic ion formula.polyatomic ion formula.

2. Write symbols. The positive ion first 2. Write symbols. The positive ion first and negative ion second.and negative ion second.

3. Put polyatomic ions in parentheses if 3. Put polyatomic ions in parentheses if more than one is needed.more than one is needed.

4. Use subscripts to designate the number 4. Use subscripts to designate the number of each part for the total + and – of each part for the total + and – charges to be =charges to be =

a. Find the least common multiple of a. Find the least common multiple of both chargesboth charges

b. determine the factor needed to get b. determine the factor needed to get that charge and use that as the that charge and use that as the subscript.subscript.

a.a. Sodium sulfideSodium sulfide

b.b. Potassium iodidePotassium iodide

c.c. Lithium oxideLithium oxide

d.d. Barium fluorideBarium fluoride

e.e. Iron(III) oxideIron(III) oxide

f.f. Copper(II) Copper(II) chloridechloride

g. Sodium acetateg. Sodium acetate

h. Zinc(II) h. Zinc(II) carbonatecarbonate

i. Chromium(II) i. Chromium(II) sulfatesulfate

j. Cobalt(III) j. Cobalt(III) iodideiodide

AnswersAnswersa.a. NaNa22SS

b.b. KIKI

c.c. LiLi22OO

d.d. BaFBaF22

e.e. FeFe22OO33

f. CuClf. CuCl22

g. NaCg. NaC22HH33OO22

h. ZnCOh. ZnCO33

i. CrSOi. CrSO44

j. CoIj. CoI33

Writing names for Writing names for ionic compoundsionic compounds

1.1. Write the names of the + and - part of the Write the names of the + and - part of the formulaformula

2.2. The + part is the name of the element or The + part is the name of the element or polyatomic ionpolyatomic ion

3.3. Check the list of elements to see if it needs a Check the list of elements to see if it needs a roman numeral. If so, use the negative part of roman numeral. If so, use the negative part of the formula to figure out the positive charge on the formula to figure out the positive charge on the metal.the metal.

4.4. To name the second/- part, if it is an element To name the second/- part, if it is an element change the ending to change the ending to ““-ide-ide””

5.5. If it is a polyatomic ion, keep the name as isIf it is a polyatomic ion, keep the name as is

a. LiClb. MgCl2

c. BeOd. CaCl2

e. HgSf. SnF2

g. (NH4)3PO4

h. ZnCO3

i. Sn(OH)2

j. Li2SO4

k. KC2H3O2

AnswersAnswersa. Lithium chlorideb. Magnesium Chloridec. Beryllium oxided. Calcium Chloridee. Mercury(II)

sulfidef. Tin(II) fluoride

g. Ammonium phosphateh. Zinc(II) carbonatei. Tin(II) hydroxidej. Lithium sulfatek. Potassium acetate

Section 3: Section 3: Covalent and Covalent and Metallic BondsMetallic BondsCovalent bonds are formed when atoms Covalent bonds are formed when atoms

share one or more pairs of valence eshare one or more pairs of valence e--..

Forms between 2 nonmetals.Forms between 2 nonmetals.

Covalent bonds result in the formation Covalent bonds result in the formation of molecules.of molecules.

Define moleculeDefine molecule

Octet RuleOctet RuleAtoms combine in such a way so as to Atoms combine in such a way so as to fill the valence shell (usually that fill the valence shell (usually that means 8 emeans 8 e-- but could be just 2 e but could be just 2 e--))

How many bonds?How many bonds?The number of eThe number of e-- that that an atom needs to an atom needs to fulfill itfulfill it’’s valence s valence is equal to the is equal to the number of covalent number of covalent bonds it can form. bonds it can form.

Ex. N can make 3 Ex. N can make 3 covalent bonds covalent bonds because it has 5 ebecause it has 5 e-- in its valence shellin its valence shell

Ex. H can make 1 Ex. H can make 1 covalent bond because covalent bond because it has 1 eit has 1 e-- its its valence shell.valence shell.

Diatomic ElementsDiatomic ElementsCertain elements exist Certain elements exist as pairs in nature as pairs in nature because that is how because that is how they are most stable.they are most stable.

Di = 2Di = 2

Just remember Professor Just remember Professor BrINClHOF (Bromine, BrINClHOF (Bromine, Iodine, Nitrogen, Iodine, Nitrogen, Chlorine, Hydrogen, Chlorine, Hydrogen, Oxygen and Fluorine)Oxygen and Fluorine)

You need to memorize You need to memorize the 7 diatomic the 7 diatomic elements!!elements!!

Practice! Draw a Bohr Practice! Draw a Bohr diagram and Lewis diagram and Lewis structure for the structure for the

following:following:Water (HWater (H22O)O)

Diatomic Fluorine Diatomic Fluorine (F(F22))

Silicon Silicon tetrafluoride (SiFtetrafluoride (SiF44))

Double BondsDouble BondsWhen atoms share 2 pairs of eWhen atoms share 2 pairs of e--, it is , it is a double bonda double bond

Triple BondsTriple BondsWhen atoms share 3 pairs of eWhen atoms share 3 pairs of e--, it is , it is a triple bonda triple bond

Naming Covalent Naming Covalent CompoundsCompounds

Many compounds have common names such Many compounds have common names such as "methane", "ammonia" and "wateras "methane", "ammonia" and "water””

Simple covalent compounds can be named Simple covalent compounds can be named using prefixes to indicate how many using prefixes to indicate how many atoms of each element are in the atoms of each element are in the formula.formula.

The ending of the last (most negative) The ending of the last (most negative) element is changed to -ide.element is changed to -ide.

Naming Covalent Naming Covalent CompoundsCompounds

Prefixes:Prefixes:

Mono = 1Mono = 1

Di = 2Di = 2

Tri = 3Tri = 3

Tetra = 4Tetra = 4

Penta = 5Penta = 5

Hexa = 6Hexa = 6

*If there is just 1 of the *If there is just 1 of the firstfirst element no prefix is used element no prefix is used

PracticePracticeCOCO22

SiFSiF44

COCO

NBrNBr33

PP22OO55

BClBCl33

AnswersAnswersCOCO22 – carbon dioxide – carbon dioxide

SiFSiF44 – silicon tetrafluoride – silicon tetrafluoride

CO – carbon monoxideCO – carbon monoxide

NBrNBr33 – nitrogen tribromide – nitrogen tribromide

PP22OO55 – diphosphorus pentoxide – diphosphorus pentoxide

BClBCl3 3 - boron trichloride - boron trichloride

PracticePracticeCarbon tetrabromideCarbon tetrabromide

Phosphorus triiodidePhosphorus triiodide

BromineBromine

silicon monoxidesilicon monoxide

Silicon disulfideSilicon disulfide

AnswersAnswersCBrCBr44

PIPI33

BrBr22 (Bromine is a diatomic molecule!) (Bromine is a diatomic molecule!)

SiOSiO

SiSSiS22

Metallic BondsMetallic BondsA bond formed by the A bond formed by the attraction between attraction between positively charged positively charged metal ions and metal ions and surrounding esurrounding e--

Think of a metal as Think of a metal as being made up of being made up of positive ions with positive ions with electrons electrons ““swimmingswimming”” around keeping the around keeping the ions togetherions together

Properties of Properties of MetalsMetals

Because eBecause e-- can move freely about, can move freely about, metals have particular propeties. metals have particular propeties.

Conduct electricity wellConduct electricity well

Metals can be reshaped (ductile, Metals can be reshaped (ductile, malleable)malleable)

Metals can bend without breakingMetals can bend without breaking