Chapter 6Chapter 6Chemical Bonds and Chemical Bonds and

CompoundsCompounds

How do these skydivers stay How do these skydivers stay together? How is this similar together? How is this similar

to the way atoms stay to the way atoms stay together?together?

Objectives:Objectives:

Describe how compounds Describe how compounds are made from are made from combinations of atoms.combinations of atoms.

Explain how chemical Explain how chemical formulas represent formulas represent chemical compounds.chemical compounds.

Section 6.1Section 6.1

If we look at all the different things around If we look at all the different things around us it is easy to see that everything is not us it is easy to see that everything is not an element. But we also know that there an element. But we also know that there are just over 100 different elements and are just over 100 different elements and they make up millions of different they make up millions of different substances.substances.

How many letters in the alphabet?How many letters in the alphabet? How many words are made from those 26 How many words are made from those 26

letters?letters? Atoms are held together in compounds by Atoms are held together in compounds by

chemical bonds.chemical bonds.

Bonds determine the properties of a Bonds determine the properties of a compound.compound.

Many times the properties of Many times the properties of compounds are often different from compounds are often different from the properties that make them.the properties that make them.

EXAMPLEEXAMPLE

+ =

CALCIUM CHLORIDECALCIUM CHLORINE

CALCIUM ~ A GROUP 2 ALKALINE EARTH CALCIUM ~ A GROUP 2 ALKALINE EARTH METAL (soft, silvery metallic solid)METAL (soft, silvery metallic solid)

CHLORINE ~ A HALOGEN is a greenish CHLORINE ~ A HALOGEN is a greenish gas very poisonous to humansgas very poisonous to humans

These two come together to form a These two come together to form a product we use to melt ice that forms on product we use to melt ice that forms on streets and sidewalks.streets and sidewalks.

In every family the number of males to females varies. In this family there are 3 females to 2 males. Me, mom and my sister THE GIRLS. Dad and my brother THE BOYS. So there is a 3:2 ratio of females to males.

Atoms always combine in predictable Atoms always combine in predictable numbersnumbers

For example NHFor example NH33 is ammonia. The is ammonia. The compound ammonia always has compound ammonia always has three hydrogen atoms for every three hydrogen atoms for every nitrogen atom.nitrogen atom.

Chemical formulasChemical formulas

Chemical formulas Chemical formulas use chemical use chemical symbols to represent the atoms of symbols to represent the atoms of the elements and their ratios.the elements and their ratios.

EX) H2O CO2

HClNH3

CH4

C3H8

This chart shows the names, atoms, ratios and chemical formulas for several chemical compounds. Notice methane and propane are made from atoms

of the same elements but in different ratios.

Two totally different substances………

Propane in the tank on your grill and methane given off when cows BURP!!!!!!!!!!!!!!!!!!!

How to Write A Chemical Formula1.Find the symbols found in the compound,

write them down side by side.2.Place subscripts to the right side of

corresponding symbols (you can find subscripts by using the oxidation numbers)

3.Remember the subscript “1” is never used

Subscript: a

number

written to

the rig

ht of a

chemical symbol and

slightly below it.

It

indicates how m

any of

each element in found in

the compound.

Same elements, different Same elements, different compoundscompounds

Which one would you want to drink?

or

ReviewReview

How many different atoms are in How many different atoms are in CC1212HH2222OO1111??

Ans: 12 carbon atoms + 22 Ans: 12 carbon atoms + 22 hydrogen atoms 11 oxygen atoms = hydrogen atoms 11 oxygen atoms = 45 total atoms45 total atoms

How do properties of compounds How do properties of compounds compare with the elements that make compare with the elements that make them?them?

Ans: most of the time VERY differentAns: most of the time VERY different

If a chemical formula has no subscripts If a chemical formula has no subscripts

For example CO (carbon monoxide)For example CO (carbon monoxide)

What is the ratio of the atoms?What is the ratio of the atoms? Ans: 1 to 1Ans: 1 to 1

If COIf CO22 is carbon dioxide then is H is carbon dioxide then is H22O O Dihydrogen monoxide? No silly Dihydrogen monoxide? No silly teacher Hteacher H22O is water!!!!!!!!!O is water!!!!!!!!!

Section 2Section 2objectivesobjectives

Explain how electrons are involved in Explain how electrons are involved in chemical bonding.chemical bonding.

Describe what the different types of Describe what the different types of chemical bonds are.chemical bonds are.

Determine how chemical bonds Determine how chemical bonds affect structure.affect structure.

What are some different ways workers What are some different ways workers at the construction sites that we saw at the construction sites that we saw in downtown Atlanta connect in downtown Atlanta connect materials?materials?

Glue

Nails

screws

Chemical bonds between Chemical bonds between atoms involve electronsatoms involve electrons

Chemical bonds are the “glue” that Chemical bonds are the “glue” that holdsholds

atoms of elements togetheratoms of elements together Chemical bonds have an effect on the Chemical bonds have an effect on the

chemical and physical properties of chemical and physical properties of compoundscompounds

Transfer Please!!!!!!!!Transfer Please!!!!!!!! When a college student needs money When a college student needs money

to cover rent and other needs they to cover rent and other needs they call mom and dad and ask them to call mom and dad and ask them to transfertransfer money to their checking money to their checking account. Mom or dad calls the bank account. Mom or dad calls the bank and says they want to and says they want to transfertransfer money to their account.money to their account.

A similar thing happens when A similar thing happens when the atom of a metal transfers the atom of a metal transfers an electron to the atom of a an electron to the atom of a

nonmetal.nonmetal.

Ionic bond: a chemical bond Ionic bond: a chemical bond that involves the electrical that involves the electrical

attraction between a negative attraction between a negative ion and a positive ionion and a positive ion

Example: an atom from Group 1, like Example: an atom from Group 1, like sodium (Na) forms a positive ion Nasodium (Na) forms a positive ion Na+ + & & meets an atom from Group 17 (a Halogen)meets an atom from Group 17 (a Halogen)

chlorine (Cl) forms a negative ion Clchlorine (Cl) forms a negative ion Cl-- the the bond forms is ionic. NaCl is table salt.bond forms is ionic. NaCl is table salt.

Just like opposite ends of a magnet Just like opposite ends of a magnet attract~~~~ these oppositely charged ions attract~~~~ these oppositely charged ions attract each other. attract each other.

So how we name these So how we name these monsters?monsters?

Name the positive metal element~ Name the positive metal element~ example sodium (Na)example sodium (Na)

Next take the name of the negative, Next take the name of the negative, nonmetal element, chlorine (Cl) and nonmetal element, chlorine (Cl) and give it the ending give it the ending –ide chloride–ide chloride

Now combine the two names making Now combine the two names making that monster’s name sodium that monster’s name sodium chloride. We just call it salt!!!!chloride. We just call it salt!!!!

Let’s try some more!Let’s try some more!

What would lithium and iodine be called?What would lithium and iodine be called?

What about sodium and fluorine?What about sodium and fluorine?

And calcium and chlorine?And calcium and chlorine?

Wow that is amazing Wow that is amazing YOU YOU just learned to just learned to name ionic compounds!!!!!!!!!!!name ionic compounds!!!!!!!!!!!

Salts are formed from the Salts are formed from the positive ion of a metal and positive ion of a metal and negative ion of a nonmetal.negative ion of a nonmetal.

Not all salts are the kind we put on Not all salts are the kind we put on our French fries. That is NaCl. our French fries. That is NaCl.

Calcium chloride CaClCalcium chloride CaCl22 is put on roads is put on roads and sidewalks to melt snow and ice. and sidewalks to melt snow and ice.

The metal ion in salts give off a The metal ion in salts give off a characteristic flame color as you saw characteristic flame color as you saw in the lady liberty fireworks site.in the lady liberty fireworks site.

http://www.driveaway.com/http://www.driveaway.com/lady_liberty/liberty_dl.htmlady_liberty/liberty_dl.htm

Properties of Ionic BondsProperties of Ionic Bonds

1.1. Solid at room tempSolid at room temp

2.2. High melting and boiling point High melting and boiling point tempstemps

3.3. Dissolves easily in waterDissolves easily in water

4.4. Good Conductors, but only in waterGood Conductors, but only in water

5.5. Brittle, Crystal-like structureBrittle, Crystal-like structure

When 2 girls share the When 2 girls share the responsibilities of being head responsibilities of being head

cheerleader what do we call them?cheerleader what do we call them? They are co-head cheerleaders.They are co-head cheerleaders. A chemical bond in which a pair of electrons are A chemical bond in which a pair of electrons are

shared between two atoms is shared between two atoms is covalent bondingcovalent bonding.. The electrons spend as much time around one The electrons spend as much time around one

atom as they do the other atom. They zip back atom as they do the other atom. They zip back and forth between atoms.and forth between atoms.

Some common substances held together by Some common substances held together by covalent bonds are: covalent bonds are: carbon dioxide (COcarbon dioxide (CO22), ), methane (CHmethane (CH44) ) and several elements exist and several elements exist covalently bonded to themselves. Hcovalently bonded to themselves. H22, , NN22, O, O22, F, F22, , ClCl22, Br, Br22, & I, & I22..

Covalent BondsCovalent Bonds A group of atoms held together by covalent A group of atoms held together by covalent

bonds is called a bonds is called a moleculemolecule..

Properties of Covalent BondsProperties of Covalent Bonds

1.1. Lower Melting Point & Boiling Point Lower Melting Point & Boiling Point TempsTemps

2.2. Will NOT dissolve in waterWill NOT dissolve in water

3.3. Does NOT conduct electricityDoes NOT conduct electricity

Polar covalent bondsPolar covalent bonds A covalent bond in which the bonds A covalent bond in which the bonds

are shared unequally.are shared unequally. Water is a perfect example of a polar Water is a perfect example of a polar

covalent bond. That is why water is covalent bond. That is why water is a good solvent and we take a bath in a good solvent and we take a bath in it!! It has both positive and negative it!! It has both positive and negative parts.parts.

So What does Polar Mean?So What does Polar Mean? Anything that has two extremes (like Anything that has two extremes (like

a magnet)a magnet) Polar Covalent Bonds occur when the Polar Covalent Bonds occur when the

molecule is asymmetrical. molecule is asymmetrical. This causes one end of the molecule This causes one end of the molecule

to be more positive & and the other to be more positive & and the other more negativemore negative

Review section 2Review section 2 What part of an atom is involved in What part of an atom is involved in

bonding?bonding? Ans: the electron cloud (ie valence Ans: the electron cloud (ie valence

electrons)electrons) Compare ionic and covalent bonds.Compare ionic and covalent bonds. Ionic: gaining/losing electronsIonic: gaining/losing electrons Covalent: sharing electronsCovalent: sharing electrons A polar covalent bond forms when?A polar covalent bond forms when? ans: two atoms share electrons unequallyans: two atoms share electrons unequally

Section 3 Section 3 Substances’ properties depend on their Substances’ properties depend on their

bondsbonds

Metals have unique bonds. They slide Metals have unique bonds. They slide easily past each other giving metals easily past each other giving metals their useful qualities (ie malleable, their useful qualities (ie malleable, ductile, shiny and good conductors)ductile, shiny and good conductors)

Properties of metals are determined Properties of metals are determined by metallic bonds.by metallic bonds.

Metallic Bond-Metallic Bond- a covalent bond with a covalent bond with equal sharing of electrons with metal equal sharing of electrons with metal elements (Non-Polar)elements (Non-Polar)

Properties of MetalsProperties of Metals

Good Conductors of electric current Good Conductors of electric current & heat& heat

Have high Melting pointsHave high Melting points Except Mercury, all metals are solid Except Mercury, all metals are solid

at room temperature.at room temperature. Easily shaped & drawn into a wireEasily shaped & drawn into a wire

Metallic BondsMetallic Bonds

In metallic compounds, atoms can In metallic compounds, atoms can slide past one another. It is as if the slide past one another. It is as if the atoms are swimming in a pool of atoms are swimming in a pool of surrounding electrons.surrounding electrons.

Pounding the metal simply moves Pounding the metal simply moves these atoms into other positions.these atoms into other positions.

This makes metals ideal for making This makes metals ideal for making coins!coins!

RememberRemember

Ionic Compounds:Ionic Compounds: Made when a positive ion (Metal) bonds Made when a positive ion (Metal) bonds

with a negative ion (Nonmetal)with a negative ion (Nonmetal) Dissolve easily in waterDissolve easily in water Good conductors of electricity (Nerve Good conductors of electricity (Nerve

signals)signals)

RememberRemember

Covalent BondsCovalent Bonds Occur between Occur between 2 nonmetals2 nonmetals Atoms covalently bonded form Atoms covalently bonded form

MoleculesMolecules Melts easilyMelts easily Does notDoes not dissolve in water dissolve in water Poor conductorsPoor conductors

Bonds can make elements look Bonds can make elements look different.different.

Carbon atoms all make up these Carbon atoms all make up these substances, So how are they all substances, So how are they all

different?different?

copper diamond fragment

graphite fragment

Carbon Can Exist as a Carbon Can Exist as a Diamond, Graphite, and Diamond, Graphite, and

FullereneFullerene Diamonds are the hardest natural Diamonds are the hardest natural

substance.substance. Made up of Carbon atoms that are Made up of Carbon atoms that are

covalently bonded to 4 other carbon covalently bonded to 4 other carbon atoms.atoms.

DiamondsDiamonds The Cullinan I, a pear The Cullinan I, a pear

shaped diamond weighing shaped diamond weighing 530.20 carats is also known 530.20 carats is also known as the Star of Africa. as the Star of Africa. Cullinan I was placed by Cullinan I was placed by King Edward in the King Edward in the Sovereign's Royal Sceptre Sovereign's Royal Sceptre as part of the Crown Jewels, as part of the Crown Jewels, and it is now on display in and it is now on display in the tower of London. the tower of London. Estimated value of Cullinan Estimated value of Cullinan I is over $400 million!I is over $400 million!

GraphiteGraphite

Dark, Slippery component of pencil Dark, Slippery component of pencil “lead”“lead”

Each Carbon atoms bond to three Each Carbon atoms bond to three other atoms to form a 2 dimensional other atoms to form a 2 dimensional layer.layer.

FullereneFullerene

Third form of CarbonThird form of Carbon Buckminsterfullerene has molecules Buckminsterfullerene has molecules

shaped like a soccer ball.shaped like a soccer ball. Man-made carbon molecule.Man-made carbon molecule. Ranges from 20-100 atoms per Ranges from 20-100 atoms per

moleculemolecule

reviewreview

Three forms of carbon are?Three forms of carbon are? Ans: diamond, graphite and Ans: diamond, graphite and

fullerenefullerene Metallic bonds make many metals?Metallic bonds make many metals? ans: good conductors of electricityans: good conductors of electricity