Unit II: Atoms Molecules & Ions - Linn–Benton …cf.linnbenton.edu/mathsci/physci/reedb/upload/Unit 2...Unit II: Atoms Molecules & Ions A. The Periodic Table B. Why and how compounds

Unit II: Atoms Molecules & IonsUnit II: Atoms Molecules & IonsA.A. The Periodic TableThe Periodic TableB.B. Why and how compounds formWhy and how compounds formC.C. Rules for writing ionsRules for writing ionsD.D. Writing formulas and naming Writing formulas and naming

compoundscompounds1.1. Binary compoundsBinary compounds2.2. Non-binary compoundsNon-binary compounds3.3. Formula writing & naming of acids and Formula writing & naming of acids and

basesbases

E.E. Chemical BondingChemical Bonding

Two general groups of elementsTwo general groups of elements

MetalsMetals Good conductors of heat & electricityGood conductors of heat & electricity Shiny, ductile, malleableShiny, ductile, malleable Lose electrons to form positive ions Lose electrons to form positive ions

NonmetalsNonmetals Poor conductorsPoor conductors Gain electrons to form negative ionsGain electrons to form negative ions Dull and without lusterDull and without luster

2-A

Antimony Arsenic

Tin Germanium

Sulfur

Iodine

2-A

Why and How Compounds FormWhy and How Compounds Form

N

e

P

P

N

e

2-B

How Ionic Compounds FormHow Ionic Compounds Form

An atom losing electrons become positively An atom losing electrons become positively charged (cation)charged (cation)

An atom gaining electrons becomes negatively An atom gaining electrons becomes negatively charged (anion)charged (anion)

Anions and cations attract each other and form Anions and cations attract each other and form compounds, lowering their total energycompounds, lowering their total energy

2-B

2-B

N

e

PPN

e

N PN N

e

PPN

e

NP

PN

NP

PNN

PPN

e

ee

e

ee

e

Lithium Flourine

e

Ionic Bonding

e

Energy Energy

Li1+ F1-

2-B

N

e

PPN

e

NP

PN

NP

PNN

PPN

e

ee

e

ee

e

e

N

e

PPN

e

N PN

Li1+

F1-

Lower total energy

Ionic Bonding

How Covalent Compounds FormHow Covalent Compounds Form

2-B

P

e

P

e

Lower total energy

MetalsMetals

NonmetalsNonmetals

CationsCations

AnionsAnionsIonic CompoundsIonic Compounds

NonmetalsNonmetals NonmetalsNonmetals

MetalsMetals MetalsMetals

+

+

Covalent CompoundsCovalent Compounds

Homogeneous MixturesHomogeneous Mixtures

2-B

Rules for Writing IonsRules for Writing Ions

Group IAGroup IA Alkali metalsAlkali metals +1+1Group IIAGroup IIA Alkaline earth metalsAlkaline earth metals +2+2Group IIIAGroup IIIA Aluminum groupAluminum group +3+3

Group VIIAGroup VIIA HalogensHalogens -1-1Group VIAGroup VIA Oxygen groupOxygen group -2-2Group VAGroup VA Nitrogen groupNitrogen group -3-3

2-C

Writing Formulas and Naming Writing Formulas and Naming Binary CompoundsBinary Compounds

1.1. Fixed oxidation state metals + nonmetalsFixed oxidation state metals + nonmetals2.2. Variable oxidation state metals + Variable oxidation state metals +

nonmetalsnonmetals3.3. Nonmetals combined with nonmetals in Nonmetals combined with nonmetals in

covalent compoundscovalent compounds

2-D

Binary ionic compounds (metals Binary ionic compounds (metals with fixed oxidation states)with fixed oxidation states)

First name the metal then…First name the metal then…

Use the root of the nonmetal with an –ide Use the root of the nonmetal with an –ide endingending

Na+ + Cl- = NaCl

Sodium + Chlorine = Sodium Chloride

Example…….

2-D

Lecture Problems: II-2 (pg.59)Lecture Problems: II-2 (pg.59)

Write the names of the following.Write the names of the following.A.A. KK22OO

B.B. AlPAlP

Use Ionic charges to write the formula of the following Use Ionic charges to write the formula of the following binary compounds.binary compounds.

C.C. sodium sulfidesodium sulfideD.D. calcium nitride calcium nitride

potassium oxidealuminum phosphide

Na2S

Ca3N2

2-D

Binary ionic compounds (metals Binary ionic compounds (metals with variable states)with variable states)

First name the metal followed by its First name the metal followed by its oxidation state in Roman Numerals inside oxidation state in Roman Numerals inside parenthesesparentheses

Then add the root of the nonmetal with an Then add the root of the nonmetal with an ––ide endingide ending

Note: You must know the oxidation state of the metal to Note: You must know the oxidation state of the metal to correctly name the compound!correctly name the compound!

2-D

Lecture Problems: II-3 (pg. 61)Lecture Problems: II-3 (pg. 61)

A.A. iron (II) fluorideiron (II) fluoride

B.B. lead (II) chloridelead (II) chloride

C.C. CuBrCuBr22

D.D. NiO NiO

FeF2

PbCl2

copper (II) bromide

nickel (II) oxide

2-D

Binary covalent compoundsBinary covalent compounds

Name the first nonmetal using a prefix to Name the first nonmetal using a prefix to indicate how many atoms are presentindicate how many atoms are present

Then name the second nonmetal using a Then name the second nonmetal using a prefix to identify quantity, and the –ide prefix to identify quantity, and the –ide endingending

Notes: Notes: 1. Drop the “mono” prefix from the element named first1. Drop the “mono” prefix from the element named first2. Name the element located lower or to the left on the periodic 2. Name the element located lower or to the left on the periodic table first table first

2-D

Covalent Compound PrefixesCovalent Compound Prefixes

1 = mono1 = mono 6 = hexa6 = hexa2 = di2 = di 7 = hepta7 = hepta3 = tri3 = tri 8 = octa8 = octa4 = tetra4 = tetra 9 = nona9 = nona5 = penta5 = penta 10 = deca10 = deca

Drop the ‘mono’ prefix from the first element Drop the ‘mono’ prefix from the first element namednamed

Lecture Problems: II-4 (pg. 62)Lecture Problems: II-4 (pg. 62)

A.A. NN22OO44

B.B. PP44SS1010

C.C. carbon dioxidecarbon dioxideD.D. trisulfur heptafluroidetrisulfur heptafluroideE.E. phosphorus pentachloride phosphorus pentachloride

dinitrogen tetraoxidetetraphosphrus decasulfide

CO2

S3F7

PCl5

2-D

Non-Binary CompoundsNon-Binary Compounds

Generally consist of a cation with a Generally consist of a cation with a polyatomic anionpolyatomic anion

May also contain polyatomic cations with May also contain polyatomic cations with mono or polyatomic anionsmono or polyatomic anions

2-D

Polyatomic ions with -1 chargePolyatomic ions with -1 charge

OHOH-- hydroxidehydroxideCNCN-- cyanidecyanideNONO33

-- nitratenitrate

NONO22-- nitritenitrite

CC22HH33OO22-- acetateacetate

MnOMnO44-- permanganatepermanganate

HCOHCO33-- bicarbonatebicarbonate

HSOHSO44-- bisulfatebisulfate

ClOClO-- hypochloritehypochloriteClOClO22

-- chloritechlorite

ClOClO33-- chloratechlorate

ClOClO44-- perchlorateperchlorate

2-D

See page 64

You will need to know them

Other Negative Polyatomic IonsOther Negative Polyatomic Ions

COCO33 2-2- carbonatecarbonate

SOSO44 2-2- sulfatesulfate

SOSO33 2-2- sulfitesulfite

CrOCrO44 2-2- chromatechromate

CrCr22OO77 2-2- dichromatedichromate

POPO44 3-3- phosphatephosphate

2-D

Positive Polyatomic IonsPositive Polyatomic Ions

NHNH44 ++ ammoniumammonium

HgHg22 2+2+ mercury(I)mercury(I)

2-D

Types of Compounds with Types of Compounds with Polyatomic IonsPolyatomic Ions

Metal of fixed oxidation state with Metal of fixed oxidation state with polyatomic anionpolyatomic anion

Metal with variable oxidation state with Metal with variable oxidation state with polyatomic anionpolyatomic anion

Polyatomic cation with monoatomic anionPolyatomic cation with monoatomic anion

Polyatomic cation with polyatomic anionPolyatomic cation with polyatomic anion

Metal of fixed oxidation state with a Metal of fixed oxidation state with a polyatomic ionpolyatomic ion

Name the metal, then name the Name the metal, then name the polyatomic ionpolyatomic ion

You must make sure to balance the You must make sure to balance the charges between ionscharges between ions

If multiple polyatomic ions are needed, If multiple polyatomic ions are needed, use () to describe how many are needed.use () to describe how many are needed.

2-D

ExamplesExamplesAluminum sulfateAluminum sulfate

Calcium hydroxideCalcium hydroxide

Barium phosphateBarium phosphate

Sodium bicarbonateSodium bicarbonate

Al2(SO4)3

Ca(OH)2

Ba3(PO4)2

NaHCO3

See Lecture Problem II-5 on Page 66 for more practice.

Compounds with a variable Compounds with a variable oxidation state metal and a oxidation state metal and a

polyatomic anionpolyatomic anion

Name the metal first, followed by the Name the metal first, followed by the oxidation state (in Roman numerals)oxidation state (in Roman numerals)

Then add the name of the polyatomic ionThen add the name of the polyatomic ion

ExamplesExamplescopper (II) sulfatecopper (II) sulfate

tin (IV) nitratetin (IV) nitrate

nickel (III) bisulfatenickel (III) bisulfate

titanium (IV) dichromatetitanium (IV) dichromate

CuSO4

Sn(NO3)4

Ni(HSO4)3

Ti(Cr2O7)2


Compounds having a polyatomic Compounds having a polyatomic cation and monoatomic anioncation and monoatomic anion

Name the positive polyatomic ion first, Name the positive polyatomic ion first, then the anion using the –ide endingthen the anion using the –ide ending

Examples and LP II-7 (pg. 67):

NH4I

ammonium oxide

ammonium iodide

(NH4)2O

Polyatomic ions with other Polyatomic ions with other polyatomic ionspolyatomic ions

Name the positive polyatomic ion first, then Name the positive polyatomic ion first, then the negative polyatomic ion.the negative polyatomic ion.

Examples:Examples:ammonium carbonateammonium carbonateammonium nitrateammonium nitratemercury (I) bicarbonatemercury (I) bicarbonate

(NH4)2CO3

NH4NO3

Hg2(HCO3)2


Naming Acids and BasesNaming Acids and Bases

Acids are substances that release Acids are substances that release hydrogen ions in water.hydrogen ions in water.

Binary acidsBinary acidsFormed for a hydrogen cation and an ‘ide’ anionFormed for a hydrogen cation and an ‘ide’ anion

Ternary acidsTernary acidsFormed from a hydrogen cation and an ‘ate’ anionFormed from a hydrogen cation and an ‘ate’ anion

Binary AcidsBinary Acids

Binary acids are formed when an anion having Binary acids are formed when an anion having the –ide ending is paired with a hydrogen the –ide ending is paired with a hydrogen cation.cation.

To write the name use the ‘hydro’ root name of To write the name use the ‘hydro’ root name of the –ide anion followed by ‘ic acid’the –ide anion followed by ‘ic acid’

Examples:Examples: HClHCl(aq)(aq) hydrochloric acidhydrochloric acid

HFHF(aq)(aq) hydrofloric acidhydrofloric acid

HH22SS(aq)(aq) hydrosulfuric acidhydrosulfuric acid

Ternary AcidsTernary Acids Consist of three different kinds of atomsConsist of three different kinds of atoms Formed by making a compound from anFormed by making a compound from an -ate anion and a H-ate anion and a H++ cation cationTo name the compound drop the –ate and To name the compound drop the –ate and

add –ic acidadd –ic acid

Examples:Examples:HH22SOSO4(aq)4(aq) sulfuric acid sulfuric acid (from sulfate)(from sulfate)

HH22COCO3(aq)3(aq) carbonic acid carbonic acid (from carbonate)(from carbonate)

BasesBasesOne definition of a base is that it produces OHOne definition of a base is that it produces OH--

(aq)(aq) ions when dissolved in water.ions when dissolved in water.

Bases are often formed by making a compound Bases are often formed by making a compound of a cation in combination with the OHof a cation in combination with the OH-- anion anion

Bases react with acids to form water Bases react with acids to form water (neutralization)(neutralization)

Bases are named just as with the polyatomic Bases are named just as with the polyatomic ions. (ternary compounds with hydroxide anion)ions. (ternary compounds with hydroxide anion)

Example: NaOH is sodium hydroxide

Part E: Chemical BondingPart E: Chemical Bonding

In review:In review:Atoms are made up of a positive nucleus and Atoms are made up of a positive nucleus and

negative electrons surrounding it.negative electrons surrounding it.

The chemical bonding properties of an element The chemical bonding properties of an element are largely determined by the electronsare largely determined by the electrons

The periodic table is organized in order of The periodic table is organized in order of increasing atomic numberincreasing atomic number


In review:In review:Atoms may either gain or loose electrons during Atoms may either gain or loose electrons during

bonding, forming ionsbonding, forming ions

Metals are the elements with the greatest Metals are the elements with the greatest tendency to loose electrons (cations)tendency to loose electrons (cations)

Nonmetals are the elements that tend to gain Nonmetals are the elements that tend to gain electrons (anions)electrons (anions)


Electrons around an atom are arranged in Electrons around an atom are arranged in what we call energy levels.what we call energy levels.

The 1The 1stst energy level is closest to the nucleus energy level is closest to the nucleus

As the energy levels increase they get further As the energy levels increase they get further from the nucleus and closer togetherfrom the nucleus and closer together

Lewis StructuresLewis Structures

Lewis Structures provide a simple way to Lewis Structures provide a simple way to show the electrons in the outermost show the electrons in the outermost energy level.energy level.

We don't write Lewis Structures for the We don't write Lewis Structures for the transition elements, only the major groups transition elements, only the major groups (group A) elements.(group A) elements.


For a Group A element in its neutral state For a Group A element in its neutral state the number of valence electrons is equal the number of valence electrons is equal to its group number.to its group number.

O F Ne

oxygen fluorine neon

Ionic Bonds with Lewis Ionic Bonds with Lewis StructuresStructures

FK FK+ -

KF

Let's practice drawing Lewis dot structures for the following ionic compounds. (Fill in on page 75)

AlCl3

Na2O Ga

2S

3

Lewis Structures for Covalent Lewis Structures for Covalent BondingBonding

In a covalent compound each atom attains In a covalent compound each atom attains stability by sharing electrons to fill its stability by sharing electrons to fill its valence shell.valence shell.

Most atoms obey the octet rule: Stability is Most atoms obey the octet rule: Stability is obtained when 8 electrons occupy an obtained when 8 electrons occupy an atoms valence shellatoms valence shell

Lewis Structures for Covalent Lewis Structures for Covalent Bonding: The MethodBonding: The Method

1. Look at the Lewis structure for each 1. Look at the Lewis structure for each atom in the molecule and add all valence atom in the molecule and add all valence electrons.electrons.

ClCl 7+7 = 14 electrons


2. Divide the number of valence electrons 2. Divide the number of valence electrons by 2, to get the number of electron pairs by 2, to get the number of electron pairs in the molecule. in the molecule.

ClCl 7+7 = 14 electrons

14 valence electrons / 2 = 7 electron pairs


3. Draw a single line between each atom to 3. Draw a single line between each atom to signify a pair of bonding electronssignify a pair of bonding electrons

ClCl

7 electron pairs – 1 bonding pair = 6 electron pairs

4. Subtract the bonding pair(s) from the 4. Subtract the bonding pair(s) from the total electron pairs.total electron pairs.


5. Arrange the remaining pairs around the 5. Arrange the remaining pairs around the bonded atoms, alternating between atomsbonded atoms, alternating between atoms

ClCl

6. Now make sure each atom has an 6. Now make sure each atom has an octect, and that you have placed all octect, and that you have placed all electrons.electrons.

Lewis Structures for Covalent Lewis Structures for Covalent CompoundsCompounds

Now lets try some slightly more complicated Now lets try some slightly more complicated molecules.....molecules.....

OFOF22 NHNH

33

What happens when some What happens when some atoms can't fill their octet?atoms can't fill their octet?

Let's consider the compound sulfur dioxide.Let's consider the compound sulfur dioxide.

18 valence electrons = 18 valence electrons = 9 electron pairs9 electron pairs

Sulfur will be our central atomSulfur will be our central atom

SO2

O S O


9 electron pairs – 2 bonding pairs = 9 electron pairs – 2 bonding pairs = 7 electron pairs7 electron pairs

Now we place the remaining electron pairs...Now we place the remaining electron pairs...

O S O


Do all the atoms have a full octet???Do all the atoms have a full octet???

O S O

NO! Sulfur only has 6 electrons in its valence shell

Now all atoms have a full octet !Now all atoms have a full octet !

Now let's try: CONow let's try: CO22 O O

33 HCN SO HCN SO33

Lewis Structures for polyatomic Lewis Structures for polyatomic ionsions

Sometimes multiple bonds will not provide Sometimes multiple bonds will not provide each atom with a full octet. each atom with a full octet.

In some cases electrons will be given up or In some cases electrons will be given up or taken in order to fill the octets, creating taken in order to fill the octets, creating ions.ions.

For Example: NO3

- OH

-NH

4

+


Lewis structures:Lewis structures:Provide an easy way to visualize valence Provide an easy way to visualize valence

electronselectronsShow us how atoms are bonded together in Show us how atoms are bonded together in

compoundscompounds

Lewis structures Lewis structures do not telldo not tell us the actual us the actual molecular shape of a compound. molecular shape of a compound.

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Unit II: Atoms Molecules & Ions - Linn–Benton …cf.linnbenton.edu/mathsci/physci/reedb/upload/Unit 2...Unit II: Atoms Molecules & Ions A. The Periodic Table B. Why and how compounds