8/12/2019 Chem 101 Ch 3,4,5

1/59

Chapter 3. Stoichiometry

3.1. Introduction

3. 2. Atomic Masses

3.3. The Mole

3.4. The Molar Mass

3.5. Percent Composition of Compounds

3.. !eterminin" the #ormula of a compound

3.$. Chemical %&uations

3.'. (alancin" Chemical %&uations

3.). Stoichiometric Calculations

3.1*. Calculations in+ol+in" a limitin" ,eactant and a percent yield

1

8/12/2019 Chem 101 Ch 3,4,5

2/59

3. 1. Introduction

Chemical reactions have a profound effect on our live.

- Foods transformed to energy.

- cancer is induced in humans by substances in our environment.

Reactions involved the quantities of materials consumed and produced. Thisarea of study is called chemical stoichiometry.

To understand chemical stoichiometry you must first understand the concept ofrelative masses.

3.2. Atomic Masses

The first quantitative information about atomic masses came from thework of alton! "ay-#ussac! #avoisier! $vogadro and %er&elius.

' mass of 1()1amu*

The modern system of atomic masses is based on carbon twelve 1+C as a

standard in this system. 1+C is assigned a mass of e,actly 1+ atomic massunits 'amu*. The masses of other atoms are given relative to this standard.

Carbon 'C* /./0 1+C 1.110 12C 34.410 15C6

Carbon atomic mass ) 1+.41 amu 'also called average atomic mass*

7nit ) atomic mass unit. amu or dalton.

$bsolute si&es of atoms8

9ass of ( atom) 1.::4;5 , 14-+5g.

article Charge 9ass 'g* 9ass 'amu*

+

8/12/2019 Chem 101 Ch 3,4,5

3/59

>roton ?1 1.:@+@,14-+5 1.44@2

Aeutron Aeutral 1.:@;4,14-+5 1.44/@

Blectron -1 .14,14-+/ ;.5/: , 14-5

#BA"T( = $A"TRD9 'E* ) 14-14m

Typical atomic dimensions are 1 to ; ,14-14m which corresponds to 1 to ; E.

3.2.1. A+era"e Atomic Mass

Pro-lem

2

8/12/2019 Chem 101 Ch 3,4,5

4/59

Aaturally occurring chlorine has two isotopes! 2;1@Cl! 2@1@Cl. The 2;-Cl isotopehas a relative atomic mass of 25.://amu and an abundance of @;.@@0 andthe 2@-Cl isotope has a relative atomic mass of 2:.:;amu and anabundance of +5.+20. Calculate the average atomic mass of Cl.

Solution

$verage $tomic 9ass of Cl ) '4.@;@@,25.:;* ?

'.+5+2,2:.:;*

) 2;.5;+@ umaatom

3.2.2. Molecular Mass

The molecular mass is the summery of the atomic masses of the atoms thatmake up the molecule.

B,ample. The chemical formula for water is CD+

9ass of C ) 1+.41 amu

9ass of D ) 1;. amu

Gts relative molecular mass ) '1+.41* ? +'1;.*

) 52. amu

3.2.3. ,elati+e Atomic Mass

$ relative scale has been developed to compare the relative masses of

atoms. The $TD9GC 9$ of an atom is its relative mass on this scale.

Carbon- 1+ '1+C* has been set as the standard and assigned a

RB#$TG

8/12/2019 Chem 101 Ch 3,4,5

5/59

The relative molecular mass is the sum of the relative atomic masses ofthe atoms that make up the molecule.

B,ample! the chemical formula for water is (+D

Gts relative molecular mass

) + '1.44@5* ? 1;.5 ) 1/.41;2

3.3. The Mole

$ mole has been defined as a unit containing :.4++12@ , 14 +2 ! $vogadroHsnumber! atoms or molecules. Dne mole of any atom or molecule contains thesame number of atoms or molecules.

$vogadroIs Aumber

$vogadroIs number8 the number of atoms in e,actly 1+ g of 1+C.

Ao) :.4++12@ , 14+2

1mole 1+C weigts 1+g and contains A4atoms.

odium 'Aa* has a relative atomic mass of ++./@@

Gf Aoatoms of 1+C have a mass of 1+g then! the mass of Ao atoms of sodiummust be '++./@@*1+ ,1+g ) ++./@@ g

1mole of sodium weigts ++./@@g

The mass! in grams! of Aoatoms of $AJ element is numerically equal to the

relative atomic mass of that element.

ame applies to molecules.

ince the relative molecular mass of water is 1/.41;+! the mass of A owatermolecules is 1/.41;+g.

;

8/12/2019 Chem 101 Ch 3,4,5

6/59

%ercise 1. Calculating number of atom

$ silicon chip used in an integrated circuit of a microcomposer has a mass of;.:/mg how many silicon 'i* atoms are present in the chipK

9olar mass of silicon ) 9i) +/.4g

olution

The strategy for doing this problem is to convert from milligrams of silicon tograms of silicon then to moles of silicon and finally to atom of silicon.

%ercise 2.

How many moles and atoms of Fe are there in 8.232 g of Fe? (M Fe=

55.85g.mol-1)

olution

:

8/12/2019 Chem 101 Ch 3,4,5

7/59

%ercise 3.

(ow many grams of water are there in 4.+444 moles of waterK '9(+D)1/.41;g.mol-1*

olution

4.+444 mol (+D , 1/.41; g.mol-1(+D ) 2.:42 g (+D

3.4. The Molar Mass

The 9olar 9ass is the mass! in grams! of one mole of atoms or molecules isnumerically equal to relative atomic or molecular masses.

(ence 1 mole of Aa weighs ++.// g! 1 mole of (+D weighs 1/.41;2 g org.mol-1.

@

8/12/2019 Chem 101 Ch 3,4,5

8/59

8/12/2019 Chem 101 Ch 3,4,5

9/59

Mass percent of an element/

For iron in iron 'GGG* o,ide! 'Fe+D2*

%mpirical #ormulas

The simplest! whole-number ratio of atoms in a molecule is called the'empirical formula*.

Can be determined from percent composition or combiningmasses.

The molecular formula is a multiple of the empirical formula.

molecular formula ) 'empirical formula*n n ) integer6

molecular formula ) C:(: ) 'C(*:

empirical formula ) C(

B,amples

(ydrogen >ero,ide

9olecular formula ) (+D+

Bmpirical formula ) (D

%en&ene

massmassof element incompound

massofcompound% = 100

mass Fe% .

..= =

11169

15969100% 6994

8/12/2019 Chem 101 Ch 3,4,5

10/59

9olecular formula ) C:(:

Bmpirical formula ) C(

"lucose

9olecular formula ) C:(1+D:

Bmpirical formula ) C(+D

%mpirical #ormula !etermination

ince mass percentage gives thenumber of grams of a particular element per 144g of compound! basethe calculation on 144g of compound! each percent will then representthe mass in grams of that element.

etermine the number of mole of each element present in 144g ofcompound using the atomic masses of the elements present.

ivide each value of the number of moles by the smallest of the values

Gf the numbers obtained in the previous step are not whole numbers!multiply each number by an integer so that the results are all wholenumbers

%ample/

Find the empirical formula of aspirin with the given mass percent composition.

Lrite down the given quantity and its units.

"iven8 C ) :4.440

( ) 5.5/0

D ) 2;.;20

14

8/12/2019 Chem 101 Ch 3,4,5

11/59

Therefore! in 144 g of aspirin there are :4.44 g C! 5.5/ g (! and 2;.;2 gD.

Gnformation8

"iven8 :4.44 g C! 5.5/ g (! 2;.;2 g D

Lrite down the quantity to find andor its units.

Find8 empirical formula! C(yD!

Collect needed conversion factors8

1 mole C ) 1+.41 g C

1 mole ( ) 1.41 g (1 mole D ) 1:.44 g D

Lrite a solution map8

$pply the solution map8

Calculate the moles of each element.

$pply the solution map8

11

Cmol.Cg12.01

Cmol1Cg. 99640060 =

Hmol.Hg1.01Hmol1Hg.48 4444 =

Omol.Og16.00

Omol1Og5.53 22123 =

8/12/2019 Chem 101 Ch 3,4,5

12/59

Lrite a pseudoformula.

$pply the solution map8

Find the mole ratio by dividing by the smallest number of moles.

122.25

2.221

2.221

2.221

4.44

2.221

4.996

OHC

OHC

Molecular #ormulas

The molecular formula is a multiple of the empirical formula.

To determine the molecular formula! you need to know the empiricalformula and the molar mass of the compound.

3.. Chemical %&uations

1+

8/12/2019 Chem 101 Ch 3,4,5

13/59

3..1. Chemical reaction

Chemical reaction is a chemical change involves a reorgani&ation of the

atoms in one or more substances.$ representation of a chemical reaction8

C+(;D( 'l* ? 2D+'g* +CD+'g* ? 2(+D 'l*

reactants products

A(2'g* ? D+'g* M AD'g* ? (+D'g*

Aotes that the atoms have been reorgani&ed %onds have been broken! and

new ones have been formed!

Gn a chemical reaction! atoms are neither created nor destroyed! all atomspresent in reactants are present in the products.

3.$. (alancin" Chemical %&uations

C+(;D( ? 2D+ +CD+ ? 2(+D

1 mole of ethanol reacts with 2 moles of o,ygen to produce + moles ofcarbon dio,ide and 2 moles of water

12

8/12/2019 Chem 101 Ch 3,4,5

14/59

The identities of the reactants and products must not be changed. Theformulas of the compounds must not be changed in balancing a chemicalequqtion.

%amples

15

8/12/2019 Chem 101 Ch 3,4,5

15/59

1. NNAaCl ? NN%eF+--O NNAaF ? NN%eCl+

+. NNFeCl2? NN%e2'>D5*+--O NN%eCl+? NNFe>D5

2. NN$gAD2? NN#iD( --O NN$gD( ? NN#iAD2

5. NNC(5? NND+--O NNCD+? NN(+D

;. NN9g ? NN9n+D2--O NN9gD ? NN9n

Solutions for the eamples

1. + AaCl ? 1 %eF+--O + AaF ? 1 %eCl+

+. + FeCl2? 1 %e2'>D5*+--O 2 %eCl+? + Fe>D5

2. 1 $gAD2? 1 #iD( --O 1 $gD( ? 1 #iAD2

5. 1 C(5? + D+--O 1 CD+? + (+D

;. 2 9g ? 1 9n+D2--O 2 9gD ? + 9n

3. '. Stoichiometric Calculations

1. %alance the equqtion for the reaction.

+. Convert the known mass of the reactant or product to moles of thatsubstance.

2. 7se the balanced equation to set up the appropriate molar ratios.

5. 7se the appropriate molar ratios to calculate the number of mole ofthe desired reactant or product.

;. Convert from moles back to grams if required by the problem.

Calculatin" Mass of ,eactants and Products

1;

8/12/2019 Chem 101 Ch 3,4,5

16/59

8/12/2019 Chem 101 Ch 3,4,5

17/59

3.). Calculations In+ol+in" a 0imitin" ,eactant

The limiting reactant is the reactant that is consumed first! limiting theamounts of products formed.

1@

8/12/2019 Chem 101 Ch 3,4,5

18/59

1/

8/12/2019 Chem 101 Ch 3,4,5

19/59

8/12/2019 Chem 101 Ch 3,4,5

20/59

Chapter 4 Types of Chemical ,eactions and

Solution Chemistry

4.1. ater the common sol+ent.

4.2. The ature of A&ueous Solutions/ Stron" and ea electrolytes.

4.3. The Composition of Solutions.

4.4. Types of Chemical ,eactions.

4.5. Precipitation ,eactions.

4.. !escri-in" ,eactions in Solutions

4.$. Stoichiometry of Precipitation ,eactions

4.'. Acid(ase Titrations.

4.). 6idation,eduction ,eactions.

4.1*. (alancin" 6idation,eduction ,eactions.

4.1. ater the common sol+ent

+4

8/12/2019 Chem 101 Ch 3,4,5

21/59

Later is one of the most important substances on earth

Dne of the most valuable properties of water is its ability to dissolvemany different substances.

Later is a dissolving medium! or a solvent.

issolved substance is a solute such as salt 'AaCl! 9gF+! PAD2! Q* in

weak amount

Lhen ionic substances dissolve in water they break up into individualcations and aninons

Later is bentS or

8/12/2019 Chem 101 Ch 3,4,5

22/59

>olar water molecules interact with positive and negative ions of a saltassisting in the dissolving process.

Bthanol is very soluble in water because of the presence of similar polar D-(bond in the tow compounds.

4.2. The ature of A&ueous Solutions/ Stron" and ea electrolytes.

Dne useful property for characteri&ing a solution is its electricalconductivity.

ame aqueous solutions conduct current +ery efficiently theycontain stron" electrolytes.

Dther solutions conduct only a small current7they contain8eaelectrolytes.

ame solution permit no current flo8 they are non electrolytes.

++

8/12/2019 Chem 101 Ch 3,4,5

23/59

hen aCl dissol+es in 8ater the Cl ions and Sodium ions a9

spread randomly. The solution conducts electricity/ The solutioncontains electrolytes

'a*trong electrolytes8 ubstances completely ioni&ed in water

'b*Leak electrolytes 8 ubstances partially ioni&ed in water or contain fewions

'c*Aon electrolytes 8substances contain no ions

+2

8/12/2019 Chem 101 Ch 3,4,5

24/59

Stron" electrolytes

Salts / Totally ioni&ed in water to give cations and anoins

Stron" acids8 Totally ioni&ed in water to give (?

:Cl ::Cl :99;a&< 9 Cl;a&< 9 Cl;a&

8/12/2019 Chem 101 Ch 3,4,5

25/59

4.3. The composition of Solutions

Chemical reaction often take place when two solutions are mi,ed.

$ solution is generally composed by8

A Solute

dissolves in water 'or other solventS*

changes phase 'if different from the solvent*

is present in lesser amount 'if the same phase as the solvent*

Sol+ent

retains its phase 'if different from the solute*

is present in greater amount 'if the same phase as the solute*

The concentration of a solution can be described in many differentways. Le limit on the morality

Molarity

9olarity 'M* 8 moles of solute per volume of solution in liters

7nits8 mol.#-1

Common Terms of Solution Concentration

tandard olution8 a solution of e,act known concentration! prepared bydissolving a definite weight of solute in a volumetric flask

tock 8 routinely used solutions prepared in concentrated form.

Concentrated 8 relati"elylarge ratio of solute to solvent. ';.4 MAaCl*

ilute8 relati"elysmall ratio of solute to solvent. '4.41 MAaCl*

+;

8/12/2019 Chem 101 Ch 3,4,5

26/59

+:

8/12/2019 Chem 101 Ch 3,4,5

27/59

teps involved in the preparation of a standard aqueous solution

a* >ut a weighted amount of substances 'solute*

b* issolve the solid in water by gently swirling the flask

c* $dd more water until the level of the solution ust reaches the marketched on the neck of the flask.

!ilution /

$ddition of water 'solvent* to a concentrated solution to get a lessconcentrated one

#aw of ilution 8

91,

8/12/2019 Chem 101 Ch 3,4,5

28/59

4.4. Types of Chemical ,eactions

>recipitation reactions

$gAD2'a#* ? AaCl'a#* A"Cl's* ? AaAD2'a#*

$cid-base reactions

AaD('a#* ? (Cl'a#* AaCl'a#* ? (+D'l*

D,idation-reduction reactions

Fe+D2's* ? $l's* Fe'l* ? $l+D2's*

4.5. Precipitation ,eactions

Lhen two solutions are mi,ed! an insolu-lesubstance sometimesforms. uch a reaction is called a precipitation reaction! and the solidthat forms is called a precipitate.

%ample 1/

+/

8/12/2019 Chem 101 Ch 3,4,5

29/59

Lhen >otassium Chromate P+CrD5 is added to a solution of %ariumAitrate %a'AD2*+! a yellow precipitate of %arium Chromate %aCrD5isformed.

P+CrD5'aq*? %a'AD2*+'aq* PAD2'aq*? (aCr64;sotassiumchloride PCl! a white precipitate of ilver chloride is formed $gCl.

Simple ,ules for Solu-ility

+

?

8/12/2019 Chem 101 Ch 3,4,5

30/59

1. 9ost nitrate 'AD-2* salts are soluble.

+. 9ost alkali 'group 1$* salts and A(5?are soluble.

2. 9ost Cl-! %r-! and G- salts are soluble.

'ADT $g?! >b+?! (g++?*

5. 9ost sulfate salts are soluble.

'ADT %aD5! >bD5! (gD5! CaD5*

;. 9ost D(-salts are only slightly soluble 'AaD(! PD( are soluble!%a'D(*+! Ca'D(*+are marginally soluble.

:. 9ost

+-

! CD2+-

! CrD5+-

! >D52-

salts are only slightly soluble.4.. !escri-in" ,eactions in Solutions

1. 9olecular equation gives the overall reaction stoichiometry but notnecessarily the actual forms of the reactants and products in solution.

$gAD2'a#* ? AaCl'a#* $gCl's* ? AaAD2'a#*

+. Complete ionic equation 'all reactants and products are strong

electrolytes*$g?'a#* ? AD2-'a#* ? Aa?'a#* ? Cl-'a#* $gCl's* ? Aa?'a#* ? AD2-'a#*

2. Aet ionic equation 'show only ions that actually react*

$g?'a#* ? Cl-'a#* $gCl's*

Aa?and AD2-are spectator ions.

4.$. Stoichiometry of Precipitation ,eactions

!eterminin" of the mass of product formed

Calculate the mass of solid AaCl that must be added to 1.;4# of a4.1449 $gAD2solution to precipitate all the $g?ions in the form of$gCl.

24

8/12/2019 Chem 101 Ch 3,4,5

31/59

Solution

Lhen added to $gAD2 solution 'which contains $g? and AD2- ions*!the solid AaCl dissolves to yield Aa? and Cl- ions. Thus the mi,ed

solution contains the ions$g? AD2- Aa? Cl-

Aotes that AaAD2 is soluble and $gCl is insoluble. Therefore $gClforms according to the following net ionic equation.

$g? ? Cl- $gCl's*

Gn this case we must add enough Cl- ions to react with $g? ionspresent. Thus we must calculate the moles of $g?present in 1.; # of4.1449 $gAD2solution.

1.;4# , 4.144 mol $g?# ) 4.41; mol $g?

%ecause $g?and Cl-react in a 181 ratio! 4.1;4 mol Cl -ions AaCl arerequired. Le calculate the mass of AaCl requied as follows.

4.'. Acid(ase Titrations

%rVnsted '1/@-15@*

Acid/ a chemical entity that gives proton (?

(ase/ a chemical entity that accept proton (?

(Cl'aq*? AaD('aq* (+D'aq*? AaCl'aq*

'(?'aq*? Cl-'aq*?* ? 'Aa?'aq*? D(-'aq** (+D'aq*? Cl-'aq*? Aa?'aq*

(?'aq*? D(-'aq* (+D'l*

Performin" Calculations for Acid(ase ,eactions

1.#ist initial species in the combined solution before any reaction occur.

+.Lrite balanced net ionic equation for this reaction.

21

8/12/2019 Chem 101 Ch 3,4,5

32/59

2.Calculate moles of reactants. 7se the volume of the original solutionsand their molarities.

5.etermine the limiting reactant.

;.Calculate moles of required reactant or product.

:.Convert to grams or volume! as required.

Lhen a ust enough base is added to react e,actly with the acid in asolution we say the acid has been neutrali&ed.

Acid(ase Titrations

8/12/2019 Chem 101 Ch 3,4,5

33/59

The indicator is a weak organic acid or organic base! its color dependson acidic or basic nature of the analyte during the titration process

>henolphthaline 8 is colorless in acidic medium and pink in base

medium while 9ethyl Drange is orange in a base medium and red inacidic medium.

4.). 6idation,eduction ,eactions

2a;s< 9 Cl2;"< 2aCl ;slanckIs constant! :.:+: , 14-25

X,s-1) kg m+s-1 m) mass! in kg ) frequency! in s-1

5. 3. Atomic Spectrum of :ydro"en

Continuous spectrum8 Contains all the wavelengths of light.

#ine 'discrete* spectrum8 Contains only some of the wavelengths oflight.

The hydrogen spectrum indicates that only certain energy are allowedfor the electron in the hydrogen atom. The energy of the electron in thehydrogen atom is quanti&ed. Changes in energy between discreteenergy levels in hydrogen will produce only certain wavelengths ofemitted light.

55

8/12/2019 Chem 101 Ch 3,4,5

45/59

8/12/2019 Chem 101 Ch 3,4,5

46/59

For n) 1! the electron has more negative energy than it does for n ): meansthat the electron is more ti"htly -ound in the smallest allowed orbit.

The change in energy *% when the ele$tron falls from n=+ to n=1

is *% ) %final state - %initial state

) B1 - B:

0imits of the (ohr>s model

%ohrIs model appeared to be very promising.

The energy levels calculated by %ohr closely agreed with the values

obtained from the hydrogen emission spectrum.

Lhen %ohrIs model was applied to atoms other than hydrogen it

5:

=hc

E

8/12/2019 Chem 101 Ch 3,4,5

47/59

did not work at all.

Blectrons do not move around the nucleus in circular orbits with

quantified energy.

5.5. The ?uantum Mechanical model of the atom

The new approach for the atoms is given by the quantum mechanics

%ased on the wave properties of the electron

$t each electron is associated a function wave .

hrVdungerIs equation

) The wave function is a function of the coordinates ',! y! &* of the

electron position in 2 space

) mathematical operator

%) total energy of the atom

$ specific wave function is often called an orbital characteri&ing its

properties.

There is a fundamental limitation to ust how precisely we can know both theposition and the momentum 'mv* of a particle at a given time.

(eisenberg 7ncertainty >rinciple

Lhere , ) position m") momentum h) >lanckIs constant

The more accurately we know a particleIs position! the less accuratelywe can know its momentum.

Pro-a-ility !istri-ution

5@

H E =

x mv ( ) 4

8/12/2019 Chem 101 Ch 3,4,5

48/59

quare of the wave function probability of finding an electron at a givenposition Radial probability distribution is the probability distribution ineach spherical shell.

Cross ection of the (ydrogen 1s Drbital >robability istributionivided into uccessive Thin pherical hells 'b* The Radial >robabilityistribution

5. . ?uantum um-ers ;?

8/12/2019 Chem 101 Ch 3,4,5

49/59

=alue of

l* 1 2 3

0etter

useds p d f

Ma"netic &uantum num-er ml

has integral values between =l and l 'ml) l to -l* relates to orientation ofthe orbital in space relative to others orbitals.

5.$. 6r-ital shapes and ener"ies

The orbital means a probability distribution

5

8/12/2019 Chem 101 Ch 3,4,5

50/59

T8o ,epresentations of the :ydro"en 1s 2s and 3s 6r-itals

aThe Blectron >robability istribution

- The urface Contains 40 of the Total Blectron >robability 'thei&e of the Dribital! by efinition*

Representation of the +p orbitals

'a* The Blectron >robability istribution for a +p oribtals.

'b*The %oundary urface Representations of all Three +porbitals.

;4

8/12/2019 Chem 101 Ch 3,4,5

51/59

Representation of the 2d Drbitals'a* Blectron ensity >lots of elected 2d Drbitals

'b* The %oundary urfaces of $ll of the 2d Drbitals

Representation of the 5f Drbitals in Terms of Their %oundary urfaces

5.'. %lectron spin and the Pauli Principle

;1

8/12/2019 Chem 101 Ch 3,4,5

52/59

Gn a given atom! electrons must be differentiated one from other .

two electrons can have the same set of quantum numbers 'n! l! ml*.

Therefore! an orbital can hold only two electrons! and they must havedifferent quantum numbers.

The solution is given by the electron spin quantum number

%lectron Spin &uantum num-er ms

'ms) ?1+!-1+* relates to the spin states of the electrons.

A Picture of the Spinnin" %lectron

The Pauli Principle

two electrons can not have the same set of quantum numbers 'n! l! ml ms *.

:und>s ,ule

The lowest energy configuration for an atom is the one having the ma,imumnumber of unpaired electrons allowed by the >auli principle in a particular set

of degenerate orbitals.

5.). Polyelectronic atoms

;+

8/12/2019 Chem 101 Ch 3,4,5

53/59

The quantum mechanical model is suitable for the hydrogen atom but notvery useful for the other atoms.

The quantum mechanical model not consider the attraction and the repulsion

between electrons in polyelectronic atoms.Dne especially important difference between polyelectronic atoms and thehydrogen atom is that a given principal quantum level have the same energy'degenerate*.

For polyelectronic atoms! we find for a given principal quantum level theorbitals vary in energy as follows

Bns3 Bn,3Bnd3Bnf

Lhen electron are placed in a particular quantum level! they prefer theorbitals in the order s! p! d and then f 'lower energies*.

Drbital Bnergy #evels for the (ydrogen $tom

5. 1*. the history of the periodic ta-le

The periodic table was originally constructed to present the patternsobserved in the chemical properties of the elements

$s chemistry progressed during 1/thand 1thcenturies! it becameevident that the earth is composed of a great many elements with verydifferent properties.

;2

8/12/2019 Chem 101 Ch 3,4,5

54/59

8/12/2019 Chem 101 Ch 3,4,5

55/59

The Blectron Configurations in the Type of Drbital Dccupied #ast for theFirst 1/ Blements

%amples/ electronic confi"uration

)#/ 1s22s22p5

15P / 1s22s22p3s23p3

Blectron Configurations for >otassium Through Prypton

The Drbitals %eing Filled for Blements in arts of the >eriodic Table

;;

8/12/2019 Chem 101 Ch 3,4,5

56/59

The >eriodic Table with $tomic ymbols! $tomic Aumbers! and >artial

Blectron

Configurations.

The >osition of the Blements

;:

8/12/2019 Chem 101 Ch 3,4,5

57/59

8/12/2019 Chem 101 Ch 3,4,5

58/59

$l'g* $l?'g* ? e- G1 ) ;/4PX.mol-1

$l?'g* $l+?'g* ? e- G+ ) 1/1; P.mol-1

$l+?'g* $l2?'g* ? e- G2 ) +@54 PX.mol-1

$l2?'g* $l5?'g* ? e- G5 ) 11:44 k.mol-1

#irst ioni@ation ener"y I1/

increases from left to right across a period

decreases going down a group

%lectron affinity %a

The energy change associated with the addition of an electron to a gaseousatom.

W'g* ? e- W-'g*

Atomic ,adii

decrease going from left to right across a period

increase going down a group.

Information Contained in the Periodic Ta-le

Bach group member has the same valence electron configuration'these electrons primarily determine an atomIs chemistry*.

The electron configuration of any representative element.

Certain groups have special names 'alkali metals! halogens! etc*.

9etals and nonmetals are characteri&ed by their chemical and physicalproperties.

;/

8/12/2019 Chem 101 Ch 3,4,5

59/59