Introduction to Chemistry, Matter, Atomic theory, Nuclear Chemistry, The Periodic Table

General Chemistry General Chemistry II

CHEMISTRY 16 LectureCHEMISTRY 16 Lecture

Jose Rene L. Jose Rene L. MicorMicor

Room: A306, B102, Room: A306, B102, C114C114

CH: 1-3pm MTWFCH: 1-3pm MTWF

Chemists and the Chemists and the tools of the tradetools of the trade

a sciencea sciencedeals with the nature of deals with the nature of

matter matter study of change or alteration study of change or alteration

of substances of substances involves in the synthesis of involves in the synthesis of

new onesnew onestooltool

What is chemistry?What is chemistry?

Books?Books?Brescia, Arrents, Meislich and Turk. Brescia, Arrents, Meislich and Turk.

Fundamental ChemistryFundamental Chemistry. 3. 3rdrd ed. ed.Bucat, R. ed. Bucat, R. ed. Elements of ChemistryElements of Chemistry. Vols. . Vols.

1 and 2. Australian Academy of Science 1 and 2. Australian Academy of Science Zumdahl, S. Zumdahl, S. ChemistryChemistry. 1986. D.C. Heath . 1986. D.C. Heath

and Co.and Co.Padolina, M.C.D., Sabularse, V.C. and Padolina, M.C.D., Sabularse, V.C. and

Marquez L.A. Marquez L.A. Chemistry for the 21Chemistry for the 21stst CenturyCentury. 1995.. 1995.

Chang, R. Chang, R. ChemistryChemistry. 6. 6thth ed. ed.

The Chemist… The Chemist… or the or the

alchemistalchemistexcellent problem solverexcellent problem solvercreativecreativeconfident confident smartsmart

ReviewReview

The scientific methodThe scientific methodProperties and Properties and Structure of MaterialsStructure of Materials

Science… Science…

a disciplinea disciplinea skilla skilla knowledgea knowledgean artan art

Method… Method…

a plana plana designa designa way of doing a way of doing thingsthings

a techniquea techniquea procedurea procedure

Material… Material… a fabric or textilea fabric or textilea data or informationa data or informationan object or thingan object or thingsomething significantsomething significanta substance or mattera substance or matter

The Scientific MethodThe Scientific Method

process that lies at process that lies at the center of scientific the center of scientific inquiryinquiry

making making oobservationsbservationsformulating formulating hhypothesisypothesisperforming performing eexperimentsxperiments

Steps in the Scientific Method?Steps in the Scientific Method?

OObservations?bservations?

Water boils at 100 °C.Water boils at 100 °C.

Kristel weighs 43 kilograms.Kristel weighs 43 kilograms.

The leaves are turning yellow.The leaves are turning yellow.

The coffee is hot.The coffee is hot.

Quantitative}

Qualitative}

HHypothesis?ypothesis?

a possible a possible explanation for explanation for the observation.the observation.

EExperimentsxperiments

carried out to test the hypothesis

involves information gathering

What do you do once a What do you do once a set of hypotheses that set of hypotheses that agree with various agree with various observations is observations is obtained?obtained?

? Question ?? Question ?

They are They are assembled into a assembled into a

theorytheory

Theory… Theory…

a philosophya philosophya concepta concepta model a model a systema systema schemea scheme

TheoryTheory

often called a model, it is a set of tested hypotheses that gives an overall explanation of some phenomena

TheoriesTheories

interpretations or possible explanations

changes eventually as more information becomes available

attempts to explain observed natural behaviors

Law… Law…

a binding rulea binding rulea piece of legislationa piece of legislationa general principlea general principlea control or authoritya control or authoritya branch of knowledgea branch of knowledge

Natural Laws?Natural Laws?

a scientific trutha scientific truth a statement of a a statement of a generally observed generally observed behaviorsbehaviors a summary of what a summary of what happenshappens

Parts of scientific methodParts of scientific method

Experiment

Theory

PredictionTheory

Modified as needed

Points to Ponder?

chemists/scientists are humans sometimes/oftentimes:

prejudiceprejudice misinterprets datamisinterprets data lose objectivitylose objectivity play politicsplay politics etc., etc.etc., etc.

Points to Ponder?

chemistry/science is affected: budget and profit motives wars and politics fads and religious beliefs

Examples

Galileo was forced to recant his astronomical observations in the face of strong religious resistance

Lavoisier was beheaded because of his political affiliations

great progress in Nitrogen chemistry resulted from the desire to produce explosives to fight wars

It is the science that deals with It is the science that deals with the composition and nature of the composition and nature of matter, and the matter, and the changes/alterations which they changes/alterations which they may undergo. may undergo.

It is concerned primarily with the It is concerned primarily with the structure of atoms, its behavior structure of atoms, its behavior and the nature of the substances and the nature of the substances which these particles compose.which these particles compose.

What chemistry is?What chemistry is?

MatterMatter

What is matter?What is matter?

it is the material of the it is the material of the universeuniverse

anything that occupies anything that occupies space and has massspace and has mass

it can absorb and emit it can absorb and emit energyenergy

Classification of MatterClassification of Matter

NatureNature

StateState

CompositionComposition

Matter and Energy are related Matter and Energy are related Energy is quantized and can only Energy is quantized and can only

be transferred in discrete unitsbe transferred in discrete unitsEnergy can be gained/lost only in Energy can be gained/lost only in

integer multiples of integer multiples of hv hv (E = (E = hvhv))Energy has mass (m = E / cEnergy has mass (m = E / c22))

The nature of matterThe nature of matter

Matter can be pure Matter can be pure substances substances

Matter can consist Matter can consist of mixtures of pure of mixtures of pure substancessubstances

The nature of matterThe nature of matter

Matter can be a solid.Matter can be a solid.

Matter can be a liquid.Matter can be a liquid.

Matter can be a gas.Matter can be a gas.

The state of matterThe state of matter

Points to Ponder?

Gases have no fixed shape or Gases have no fixed shape or volume.volume.

Gases can be compressed to Gases can be compressed to form liquids.form liquids.

Liquids have no shape, but they Liquids have no shape, but they do have a measurable volume.do have a measurable volume.

Solids are rigid and have a Solids are rigid and have a definite shape and volume.definite shape and volume.

Matter is made up of Matter is made up of relatively few relatively few elementselements..

On the microscopic On the microscopic

level, matter consists of level, matter consists of

atomsatoms and and moleculesmolecules..

Composition of matterComposition of matter

Points to Ponder?

Elements Elements consist onlyconsist only of one of one type of atoms.type of atoms.

Atoms Atoms combinecombine to form to form molecules. molecules.

Molecules Molecules can consistcan consist of more of more than one type of atoms.than one type of atoms.

Molecules Molecules can have can have only one only one type of atom (an type of atom (an elementelement).).

Points to Ponder?

Molecules Molecules can havecan have more than more than one type of atom (a one type of atom (a compoundcompound). ).

If more than one atom, element, If more than one atom, element, or compound are found together, or compound are found together, then the substance is a then the substance is a mixturemixture..

Points to Ponder?

If matter If matter is notis not uniform uniform throughout, then it is a throughout, then it is a heterogeneousheterogeneous mixturemixture..

If matter is uniform If matter is uniform throughout, it is throughout, it is homogeneoushomogeneous..

Physical Physical vs.vs. Chemical Chemical ObservationsObservations

a cook/chef distinguishes sugar a cook/chef distinguishes sugar from salt by from salt by tastetaste..

many will recognize ether, ethanol many will recognize ether, ethanol and ammonia by their odor.and ammonia by their odor.

jewelers will have an obvious clue jewelers will have an obvious clue of ferric oxide by its colorof ferric oxide by its color

mercury may be recognized by its mercury may be recognized by its liquid state from other metalsliquid state from other metals

a gold miner readily distinguish a gold miner readily distinguish gold from pyrite by dissolving gold from pyrite by dissolving them into nitric acid, the latter them into nitric acid, the latter dissolves in the acid while gold dissolves in the acid while gold remains unreactive.remains unreactive.

smelters knows that iron can be smelters knows that iron can be obtained when they combined obtained when they combined hematite with coke and limestone.hematite with coke and limestone.

Physical Physical vs.vs. Chemical Chemical ObservationsObservations

Physical Physical vs.vs. Chemical Chemical ChangeChange

When a substance When a substance undergoes a physical undergoes a physical change, its physical change, its physical appearance changes. appearance changes.

Physical changes Physical changes do do notnot result in a change result in a change of composition.of composition.

When a substance changes When a substance changes its composition, it its composition, it undergoes a chemical undergoes a chemical change:change:Ex. When pure hydrogen and pure Ex. When pure hydrogen and pure

oxygen in a flask react oxygen in a flask react completelycompletely, , they form pure water. In the flask they form pure water. In the flask containing water, there is no oxygen containing water, there is no oxygen or hydrogen or hydrogen left overleft over..

Physical Physical vs.vs. Chemical Chemical ChangeChange

Points to Ponder?

If homogeneous matter If homogeneous matter can becan be separated by physical means, separated by physical means, then the matter is a then the matter is a mixturemixture..

If homogeneous matter If homogeneous matter cannot becannot be separated by separated by physical means, then the physical means, then the matter is a matter is a pure substancepure substance..

Points to Ponder?

If a pure substance If a pure substance can becan be decomposed into something decomposed into something else, then it is a else, then it is a compoundcompound..

If a pure substance If a pure substance cannot cannot bebe decomposed into decomposed into something else, then the something else, then the substance is an substance is an elementelement..

SUMMARY

Heterogeneous

Compound

Homogenous mixture

(Solution)

Element

Uniform

MATTER

Physical Separation

Homogenous

Chemical Decomposition

Pure Substances

Examples

Chemistry is a lot like love. Without chemistry, there

won’t be any rage of hormones or even couples made because they are not

in sync with each other Rudden Montecillo

Chemistry is like DOTA: Dealing of Things Aspect May mga recipes din … Dapat nagmimix ang characters

… para maganda ang product Both aim to improve, … continue

to discover and develop Both are FUN

Mark Erben A. Jaim

Chemistry:

A journey of a thousand miles that begins with a single step…

It is like a bikini, what it reveals is essential… what it conceals is vital…

Rhea May S. Tindoy

Chemistry is omnipresent … at times we find ourselves “in chemistry” with other

people Cool at creative na pag Halo ng mga Elements na nagfo2rm ng Matter It Suggests that one must TRY to study hard & excel

Sheryll Rose M. delos Reyes

• “Mystery solver” ... – Lianell Maesa• “like a shadow” … since birth… still chemistry

is with me. – Raymundo P. Villacorta Jr.

• …confuses my senses … makes me feel interested… - Maria Victoria Sario

• Chemistry is like a song. Once you learned it, you’ll find yourself enjoying & loving it – Catherine P. Suazo

• … is like SMART & Globe … “its simply AMAZING” & “makes Great Things Possible” – Melissa E. Leyva

• … is a challenge. – Glenn Mark M. Sutingco

Atomic TheoryAtomic Theory

History of ChemistryHistory of Chemistry

600 B.C.600 B.C. • highlights extraction and working of highlights extraction and working of

metals. Egyptians extracted copper, metals. Egyptians extracted copper, gold, silver and lead from their ores gold, silver and lead from their ores and work on brass and bronze.and work on brass and bronze.

• dyeing and alcoholic beverages dyeing and alcoholic beverages productionproduction

• extraction of oils and alkaloid from extraction of oils and alkaloid from plantsplants


600 - 200 B.C.600 - 200 B.C.• highlights the Greeks curiosity, intellect highlights the Greeks curiosity, intellect

and vigorous imagination. and vigorous imagination. • Original ideas and many fundamental Original ideas and many fundamental

scientific problems was recognized by scientific problems was recognized by the philosophers of Ancient Greece.the philosophers of Ancient Greece.

• Democritus, Aristotle and Leucippus are Democritus, Aristotle and Leucippus are among those Greek philosophers.among those Greek philosophers.

Greek ideasGreek ideas

All substances are made of 4 All substances are made of 4 elementselementsFire - hotFire - hotAir - lightAir - lightWater - wetWater - wetEarth - cool, heavyEarth - cool, heavy

Blend these in different Blend these in different proportions to get all substances proportions to get all substances

Chinese ideasChinese ideas

All matters constitute of 5 elementsAll matters constitute of 5 elementsMetalMetalWoodWoodWaterWaterFireFireEarthEarth

"Different combinations of earth, "Different combinations of earth, metal, wood, water and fire form metal, wood, water and fire form everything in the world." everything in the world."


"Water corresponds to moisture and "Water corresponds to moisture and the direction of down.” the direction of down.”

““Fire corresponds to blaze and the Fire corresponds to blaze and the direction of up.”direction of up.”

““Wood is curvy or straight in Wood is curvy or straight in nature.” nature.”

““Metal is unstable under fire.” Metal is unstable under fire.” ““Earth is necessary for agriculture.” Earth is necessary for agriculture.” ““Water becomes salty when Water becomes salty when

travelling down.” travelling down.”


““Fire becomes bitter when Fire becomes bitter when blazing upward.” blazing upward.”

““Wood may turn acid when it Wood may turn acid when it changes shape.” changes shape.”

““Metal may turn bitter when it Metal may turn bitter when it becomes unstable.” becomes unstable.”

““Earth may turn sweet when Earth may turn sweet when used in agriculture." used in agriculture."


400 - 1650 400 - 1650 • highlights the rise and spread of highlights the rise and spread of

alchemy, the pretended art of changing alchemy, the pretended art of changing baser metal into gold. baser metal into gold.

• the quest for the miraculous the quest for the miraculous “philosopher stone”“philosopher stone”

• many useful apparatus were perfectedmany useful apparatus were perfected• large number of new and important large number of new and important

substances were prepared/discoveredsubstances were prepared/discovered• new techniques developednew techniques developed


1400 - 1750 1400 - 1750 • highlights the development of systematic highlights the development of systematic

metallurgy by Georg Bauermetallurgy by Georg Bauer• medicinal application and preparation of medicinal application and preparation of

remedies and drugs by Paracelsusremedies and drugs by Paracelsus• Roger Bacon stressed competent Roger Bacon stressed competent

knowledge through experimentationknowledge through experimentation• Francis Bacon exposed the fallibility of Francis Bacon exposed the fallibility of

Aristotle’s doctrinesAristotle’s doctrines• relationship between pressure and relationship between pressure and

volume of gases was measured by Robert volume of gases was measured by Robert BoyleBoyle


1700 - 1777 B.C.1700 - 1777 B.C.•Georg Stahl suggested that all Georg Stahl suggested that all

combustible substances contained combustible substances contained a “fiery principle”, a “fiery principle”, phlogistonphlogiston, , which escaped as flame when which escaped as flame when heatedheated

•oxygen gas was discovered by oxygen gas was discovered by Joseph PriestleyJoseph Priestley

•quantitative and qualitative quantitative and qualitative analysis improved greatly by analysis improved greatly by Joseph Black and Olaf BergmanJoseph Black and Olaf Bergman

Who’s Next?Who’s Next?Antoine Lavoisier (1743-1794) Antoine Lavoisier (1743-1794)

overthrow completely the phlogiston overthrow completely the phlogiston theory and provided explanation of theory and provided explanation of combustion.combustion.

Joseph Proust (1754-1826) showed that Joseph Proust (1754-1826) showed that a given compound always contains a given compound always contains exactly the same proportion of exactly the same proportion of elements by weight.elements by weight.

John Dalton (1766-1844) postulated John Dalton (1766-1844) postulated that the fundamental differences that the fundamental differences among atoms are their masses.among atoms are their masses.

Dalton’s Atomic TheoryDalton’s Atomic Theory

All All mattermatter is made of tiny is made of tiny indivisibleindivisible particles called atoms.particles called atoms.

Atoms of the same element are Atoms of the same element are identical, those of different atoms are identical, those of different atoms are different.different.

Atoms of different elements combine in Atoms of different elements combine in whole number ratios to form compoundswhole number ratios to form compounds

Chemical reactions involve the Chemical reactions involve the rearrangement of atoms. No new atoms rearrangement of atoms. No new atoms are created or destroyed.are created or destroyed.

Law of Definite Law of Definite ProportionsProportions

Originally called the Proust’s lawOriginally called the Proust’s lawEach compound has a specific Each compound has a specific

ratio of elementsratio of elementsIt is a ratio by mass It is a ratio by mass Water is always 8 grams of Water is always 8 grams of

oxygen for each gram of oxygen for each gram of hydrogen hydrogen

Law of Multiple Law of Multiple ProportionsProportions

if two elements form if two elements form more than one more than one compound, the ratio of compound, the ratio of the second element that the second element that combines with 1 gram of combines with 1 gram of the first element in each the first element in each is a simple whole numberis a simple whole number

Early experiments Early experiments on atomic on atomic structurestructure

performed by J. J. Thomsonperformed by J. J. Thomsonmade a piece of equipment made a piece of equipment

called a cathode ray tube, it called a cathode ray tube, it is a vacuum tube which is a vacuum tube which emanated a “ray” when high emanated a “ray” when high voltage is applied to itvoltage is applied to it

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

Voltage source

+-

Passing an electric current makes a beam Passing an electric current makes a beam appear to move from the negative to the appear to move from the negative to the positive endpositive end

Voltage source

+-

Voltage source

By adding an electric field By adding an electric field

+

-

Voltage source

+

-

Voltage source

He found out that the moving He found out that the moving pieces were negative pieces were negative

+

-

Thomson’s ModelThomson’s Model

• Found the electronFound the electron• Couldn’t find Couldn’t find

positive (for a positive (for a while) while)

• Said the atom was Said the atom was like plum puddinglike plum pudding

• A bunch of positive A bunch of positive stuff, with the stuff, with the electrons able to electrons able to be removed be removed

The other piecesThe other pieces

Proton - positively Proton - positively charged pieces 1840 charged pieces 1840 times heavier than the times heavier than the electronelectron

Neutron - no charge but Neutron - no charge but the same mass as a the same mass as a proton.proton.

Millikan’s experimentMillikan’s experiment

Robert Millikan (1868-1953) Robert Millikan (1868-1953) performed an experiment involving performed an experiment involving charged oil drops.charged oil drops.

It allowed him to determine the It allowed him to determine the magnitude of electron chargemagnitude of electron charge

With this value together with With this value together with Thomson’s charge to mass ratio, he Thomson’s charge to mass ratio, he was able to calculate the mass of was able to calculate the mass of the electron to be 9.11 x 10the electron to be 9.11 x 10-31-31 kilogram.kilogram.

Rutherford’s experimentRutherford’s experimentErnest Rutherford (1871-1937) Ernest Rutherford (1871-1937)

experiment on alpha particles experiment on alpha particles striking thin metal foils led him to striking thin metal foils led him to postulate the nuclear atom.postulate the nuclear atom.

He did much work in He did much work in characterizing radioactivitycharacterizing radioactivity

He believed in the plum pudding He believed in the plum pudding model of the atom.model of the atom.

He wanted to see how big they are He wanted to see how big they are

Lead block

Uranium

Gold Foil

Florescent Screen

The alpha particles pass The alpha particles pass through without changing through without changing direction very much direction very much

The positive charges were The positive charges were spread out evenly. Alone spread out evenly. Alone they were not enough to they were not enough to stop the alpha particlesstop the alpha particles

Rutherford’s experimentRutherford’s experiment

He expected the alpha particles to pass through without changing direction very much

What does he What does he expected?expected?

Because he believed in the plum pudding model of the atom

WHY?WHY?

Because, he thought the mass was evenly distributed in the atom

WHY?WHY?

What really happens?

Alpha particles are deflected by it if they get close enough to a small dense, positive piece at center

+

Atom is mostly empty

The atom is The atom is mostly empty mostly empty spacespace

Two regionsTwo regionsNucleus Nucleus - -

protons and protons and neutronsneutrons

Electron cloud Electron cloud - region where - region where you might find you might find an electronan electron

Points to Ponder?

Density and the AtomDensity and the Atom

Since most of the particles went Since most of the particles went through, it was mostly empty.through, it was mostly empty.

Because the pieces turned so much, Because the pieces turned so much, the positive pieces were heavy.the positive pieces were heavy.

Small volume, big mass, big densitySmall volume, big mass, big densityThis small dense positive area is the This small dense positive area is the

nucleusnucleus

Subatomic particlesSubatomic particles

Electron

Proton

Neutron

Name Symbol ChargeRelative mass

Actual mass (g)

e-

p+

n0

-1

+1

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24

Structure of the AtomStructure of the Atom

There are two regionsThere are two regionsThe nucleus (Almost all the mass The nucleus (Almost all the mass

is concentrated)is concentrated)With protons and neutrons With protons and neutrons Positive chargePositive charge

Electron cloud (Responsible for Electron cloud (Responsible for most of the volume of an atom)most of the volume of an atom)The region where the electron can The region where the electron can

be foundbe found

Size of an atomSize of an atom

Atoms are small.Atoms are small.Measured in picometers (10Measured in picometers (10-12-12 meters) meters)

Ex. The hydrogen atom, 32 pm radiusEx. The hydrogen atom, 32 pm radiusNucleus tiny compared to atomNucleus tiny compared to atom

IFIF the atom was the size of a stadium, the atom was the size of a stadium, the nucleus would be the size of a the nucleus would be the size of a marble.marble.

Radius of the nucleus near 10Radius of the nucleus near 10-15-15m.m.

•1803 Dalton model of the atom is an indivisible, indestructible, tiny ball•1850 Evidence is accumulating that the atom is itself composed of smaller particles •1895 Wilhelm Roentgen discovered that when cathode rays struck certain materials (copper for example) a different type of ray was emitted. •1896 Henri Becquerel studied materials which would emit light after being exposed to sunlight (i.e. phosphorescent materials)

Historical SummaryHistorical Summary

•1897 J.J. Thompson measured the charge to mass ratio for a stream of electrons (using a cathode ray tube apparatus) at 1.76 x 108 coulombs/gram•1900 J.J. Thompson model of the atom consists of a sphere of positive charge within which was buried negatively charged electrons •1909 Robert Millikan was able to successfully measure the charge on a single electron (the "Milliken oil drop experiment"). This value was determined to be 1.60 x 10-19 coulombs.


•1910 Rutherford studied alpha rays, beta rays and gamma rays

Rutherford model of the atom:Most of the mass of the atom, and all its positive charge, reside in a very small dense centrally located region called the "nucleus" Most of the total volume of the atom is empty space within which the negatively charged electrons move around the nucleus

•1919 Rutherford discovers protons •1932 Chadwick discovers neutron


Greek IdeaGreek Idea

Democritus believed Democritus believed that matter is made up that matter is made up of fundamentally of fundamentally indivisible particles indivisible particles called “atomos”called “atomos”

Matter is made up of Matter is made up of indivisible (indivisible (atomosatomos) ) particlesparticles

Dalton - one type of Dalton - one type of atom for each elementatom for each element

The Nuclear AtomThe Nuclear AtomThey conclude that the atom consists of neutral, positively, and negatively charged entities.Thomson assumed all these charged species were found in a sphere.

Discovery of Atomic StructureDiscovery of Atomic Structure

Thomson’s ModelThomson’s Model

Atoms were made Atoms were made of positive stuffof positive stuff

Negative electron Negative electron floating aroundfloating around

““Plum-Pudding” Plum-Pudding” modelmodel

The Nuclear AtomThe Nuclear Atom

Rutherford carried out his experiment and deduced that if the Thomson model of the atom was correct, then his results was impossible.


Rutherford’s ModelRutherford’s Model

Discovered dense Discovered dense positive piece at positive piece at the center of the the center of the atomatom

NucleusNucleusElectrons moved Electrons moved

aroundaroundMostly empty Mostly empty

spacespace

The Nuclear AtomThe Nuclear Atom

Rutherford modified Thomson’s modelAssumed that the atom is spherical but the positive charge must be located at the centerAssumed a diffuse negative charge surrounding it.Believed moving charges Believed moving charges (electrons) should lose energy (electrons) should lose energy and fall into the nucleusand fall into the nucleus


The atom consists of positive, negative, and neutral entities (protons, electrons, and neutrons).

Protons and neutrons are located in the nucleus of the atom, which is small. Most of the mass of the atom is due to the nucleus.

Electrons are located outside of the nucleus. Most of the volume of the atom is due to electrons.

The Modern View of Atomic StructureThe Modern View of Atomic Structure

Bohr’s IdeaBohr’s Idea

Why don’t the electrons fall Why don’t the electrons fall into the nucleus?into the nucleus?

Move like planets around the Move like planets around the sun.sun.

In circular orbits at different In circular orbits at different levels.levels.

Amounts of energy separate Amounts of energy separate one level from another.one level from another.

Nuclear Nuclear ChemistryChemistry

Atomic NumberAtomic Number

represented by the letter represented by the letter

ZZ

the number of protons in the number of protons in

the nucleus of an atomthe nucleus of an atom

Mass NumberMass Number

represented by the letter Arepresented by the letter A

the total number of protons the total number of protons

and neutrons in the atomic and neutrons in the atomic

nucleus of an atomnucleus of an atom

Atomic MassAtomic Mass

is not a whole number is not a whole number because it is an average. because it is an average.

are the decimal numbers are the decimal numbers on the on the periodic tableperiodic table..

SymbolsSymbols

signsignfigurefigureiconiconmarkmarkrepresentationrepresentation

Chemical SymbolsChemical SymbolsThe complete symbol of an element The complete symbol of an element contains the symbol of the element, the contains the symbol of the element, the mass number and the atomic numbermass number and the atomic number

X Massnumber

Atomicnumber

IsotopesIsotopes

Atoms of the same Atoms of the same element can have element can have different numbers of different numbers of neutrons thus neutrons thus different mass different mass numbersnumbers

Measuring Atomic MassMeasuring Atomic Mass

Unit is the Unit is the AAtomic tomic MMass ass UUnit nit (amu)(amu)

One twelfth the mass of a carbon-One twelfth the mass of a carbon-12 atom. 12 atom.

Each isotope has its own atomic Each isotope has its own atomic mass mass

The average can be calculated The average can be calculated from percent abundances.from percent abundances.

Naming and Writing Naming and Writing IsotopesIsotopes

•Put the mass number after Put the mass number after the name of the elementthe name of the element

carbon-12carbon-12

carbon-14carbon-14

uranium-235uranium-235

C126

C146

U23592

Find the Find the

–number of protonsnumber of protons

–number of neutronsnumber of neutrons

–number of electronsnumber of electrons

–Atomic numberAtomic number

–Mass NumberMass Number

Br80 35

45

35 35

80

35

ExerciseExercise

ExerciseExerciseif an element has an atomic if an element has an atomic number of 47 and a mass number of 47 and a mass number of 108 what is the: number of 108 what is the: – Number of protonsNumber of protons– Number of neutronsNumber of neutrons– Number of electronsNumber of electrons– SymbolSymbol– Complete symbolComplete symbol

61

Ag 47

47

Ag10847

ExerciseExerciseif an element has 94 protons if an element has 94 protons and 150 neutrons what is the: and 150 neutrons what is the:

– Atomic numberAtomic number– Mass numberMass number– Number of electronsNumber of electrons– SymbolSymbol– Complete symbolComplete symbol

244

Pu 94

94

Pu24494

if an element has 78 electrons if an element has 78 electrons and 117 neutrons what is the: and 117 neutrons what is the: – Atomic numberAtomic number– Mass numberMass number– Number of protonsNumber of protons– SymbolSymbol– Complete symbolComplete symbol

ExerciseExercise

195

Pt78

78

Pt19578

Chemical FormulasChemical Formulasoften interchange with molecular formulaoften interchange with molecular formulaillustrates the method of writing and describing illustrates the method of writing and describing

molecules or compounds in atomic termsmolecules or compounds in atomic termsmakes use of chemical symbols and subscriptsmakes use of chemical symbols and subscripts

XWholenumber

Wholenumber

Y

Chemical FormulasChemical Formulas

subscripts in a chemical formula tell subscripts in a chemical formula tell us how many atoms of each element us how many atoms of each element contribute to formation of a contribute to formation of a particular molecule. particular molecule.

if the subscript is '1' it is omitted if the subscript is '1' it is omitted from the formula. from the formula.

XX1X1 2YX 2Y Ex. CO2Ex. C

Chemical FormulasChemical Formulas

Molecular FormulaMolecular FormulaEmpirical FormulaEmpirical FormulaStructural FormulaStructural Formula

Molecular FormulaMolecular Formula

refers to the refers to the actualactual number number of the different atoms which of the different atoms which comprise a single molecule comprise a single molecule of a compound. of a compound.

lists the exact recipe that lists the exact recipe that makes up the molecule. makes up the molecule.

Empirical FormulaEmpirical Formula

refers to the refers to the smallest smallest whole number ratioswhole number ratios of of atoms in a particular atoms in a particular compound. compound.

provides information only provides information only about the relative ratio of the about the relative ratio of the elements in a compound. elements in a compound.

Structural FormulaStructural Formulagives information regarding the gives information regarding the

connectivity between atoms in a connectivity between atoms in a compoundcompound

tries to give information tries to give information regarding bond length and bond regarding bond length and bond angles in a compound angles in a compound

don't necessarily give don't necessarily give information about the information about the actual actual geometrygeometry of such bonds. of such bonds.

Reactions involving the Reactions involving the nuclei of atoms.nuclei of atoms.

The spontaneous The spontaneous decomposition of the nucleus decomposition of the nucleus to form a different nucleus.to form a different nucleus.

Also known as radioactive Also known as radioactive decaydecay

RadioactivityRadioactivity

• Somatic damagedamage to the organism itself resulting in either sickness or deatheffects may appear immediately or years later, usually in the form of cancer

• Genetic damagedamage to the genetic machinery of the body

produces malfunctions in the offspring of the organism.

Effects of RadiationEffects of Radiation

• The energy of the radiation

• The penetrating ability of the radiation

• The ionizing ability of the radiation

• The chemical properties of the radiation source

Factors affecting biological Factors affecting biological effects of radiation sourceeffects of radiation source

Nuclear TransmutationNuclear Transmutation

The process of producing radioactivity artificially by bombarding an isotope with high energy particle.

Nuclear FissionNuclear Fission

the process in which a heavy nucleus (mass number > 200) divides to form smaller nuclei of intermediate mass and one or more neutrons.

accompanies by a release of large amounts of energy.

Nuclear FusionNuclear Fusion

the combining of small nuclei into larger ones

accompanied by a release of large amounts of energy

CHEMICAL REACTION NUCLEAR REACTION

1. Atoms are rearranged by the breaking and forming of chemical bonds.

2. Only electrons in atomic orbitals are involved in the breaking and forming of bonds.

3. Reactions are accompanied by absorption and release of relatively small amounts of energy.

4. Rates of reactions are influenced by temperature, pressure, conc. and catalysts.

1. Elements (or isotopes of the same elements) are converted from one to another.

2. Protons, neutrons, electrons and other elementary particle may be involved.

3. Reactions are accompanied by absorption or release of tremendous amounts of energy.

4. Rates of reactions normally are not affected by temperature, pressure, and catalysts.

The Nature of Nuclear The Nature of Nuclear ReactionsReactions

Natural RadioactivityNatural RadioactivityMain types of radiation are:Main types of radiation are:

particles (He nuclei)particles (He nuclei) particles (electrons)particles (electrons) ray (high energy ray (high energy electromagnetic radiation or electromagnetic radiation or photon.)photon.)

positrons (same mass as epositrons (same mass as e-- but but opposite chargeopposite charge

electron captureelectron capture

Nuclear SymbolsNuclear SymbolsMain types of radiation are:Main types of radiation are:

particles particles HeHe particles particles ee ray ray positrons epositrons eelectrons eelectrons e

The Uranium Decay Series

Radioactive Radioactive Decay SeriesDecay Series

What makes an isotope unstable?What makes an isotope unstable?What makes some isotopes What makes some isotopes

undergo radioactivity?undergo radioactivity?What makes isotopes unstable?What makes isotopes unstable?

?Points to Ponder??Points to Ponder?

To improve this ratio, a proton can be converted to a neutron by -particle emission. (If the nucleus lies above the belt of stability.)

If the nucleus lies below the belt of stability, the nucleus can either undergo positron emission or electron capture.

Nuclear StabilityNuclear Stability

Nuclei that contain 2, 8, 20, 50, 82 or 126 protons or neutrons are generally more stable than nuclei that do not possess these numbers.

Nuclei with even numbers of both protons and neutrons are generally more stable than those with odd numbers of these particle.

Nuclear StabilityNuclear Stability

Balancing Nuclear Balancing Nuclear ReactionReaction

Since the reactions involve Since the reactions involve the nucleus, the reaction the nucleus, the reaction equations must include equations must include information about the nucleus. information about the nucleus. Namely, it give mass numbers Namely, it give mass numbers (A) and atomic numbers (Z).(A) and atomic numbers (Z).

C126

Balance the following:

X K

X p Mg

01-

4019

42

11

2612

Na X =

Ca X =

More ProblemsMore Problems

• N + He N + He XX + H + H

• XX + He + He P + n P + n

• neutron + U-235 neutron + U-235 Ba-142 + Kr-91 Ba-142 + Kr-91 + neutrons + neutrons

Kinetics of Radioactive DecayKinetics of Radioactive Decay

= rate of decay

t = time

No = initial amount of nuclides

N = final amount of nuclides

t1/2 = Half life

tN

No

ln693.0

t2

1

Half-lifeHalf-life

The half-life of a radioactive sample is defined as the time required for the number of nuclides to reach half the original value(No/2).

Sample ProblemsSample Problems

•The remnants of an ancient fire The remnants of an ancient fire cave showed a C-14 decay rate cave showed a C-14 decay rate of 3.1 counts per minute per of 3.1 counts per minute per gram of C. Assuming that the gram of C. Assuming that the decay rate of wood is 13.6 decay rate of wood is 13.6 counts per minute per gram C, counts per minute per gram C, calculate the age of the firewood calculate the age of the firewood remnant. The half-life of C-14 is remnant. The half-life of C-14 is 5730 years.5730 years.


• Rate = Rate = N N• 3.1 counts/min g = rate at time t 3.1 counts/min g = rate at time t • 13.6 counts/min g = rate at time 013.6 counts/min g = rate at time 0

• N/NN/Noo = 0.23 = 0.23 = 1.2094 x10= 1.2094 x10-4-4 (derived from 2 (derived from 2ndnd eq.) eq.)

• ln (N/Nln (N/Noo) = -) = - t t

• ln (0.23) = -1.4697ln (0.23) = -1.4697• t = -1.4697/-1.2094x10t = -1.4697/-1.2094x10-4-4 = 12,152 yrs = 12,152 yrs


•How many disintegrations per How many disintegrations per second are there from 1.00 second are there from 1.00 mol of nuclide with each of mol of nuclide with each of the following half lives:the following half lives:12,000 yr? 12,000 yr? 12 h?12 h?12 min?12 min?12 sec?12 sec?

• How many disintegrations per How many disintegrations per second are there from 1.00 second are there from 1.00 mol of nuclide with each of the mol of nuclide with each of the following half lives:following half lives:12,000 yr? 12,000 yr? 1.1x101.1x101212 d./sec d./sec12 h?12 h? 9.7x109.7x101818 d./sec d./sec12 min?12 min? 5.8x105.8x102020 d./sec d./sec12 sec?12 sec? 3.5x103.5x102222 d./sec d./sec


•Technetium-99 is often used Technetium-99 is often used medicine to assess heart medicine to assess heart damage. Its rate constant for damage. Its rate constant for decay is known to be 1.16 x decay is known to be 1.16 x 1010-1-1/hr. What is the half-life of /hr. What is the half-life of the nuclide?the nuclide?

5.97 hr5.97 hr

Drill or QuizDrill or Quiz

•The practical limit for carbon-The practical limit for carbon-14 dating occurs when the 14 dating occurs when the activity falls to 0.20% of its activity falls to 0.20% of its original value. If the half-life of original value. If the half-life of 1414C is 5715, what is the C is 5715, what is the maximum age of the sample maximum age of the sample that can be dated using that can be dated using 1414C?C?a.a.13,000 yrs.13,000 yrs. c. 51,250 yrs.c. 51,250 yrs.b.b. 22,300 yrs.22,300 yrs. d. 107,000 yrs.d. 107,000 yrs.

The Periodic TableThe Periodic Table

HistoryHistoryJohann Dobereiner recognized a pattern in Johann Dobereiner recognized a pattern in

several groups of three elements, examples several groups of three elements, examples are chlorine, bromine and iodine.are chlorine, bromine and iodine.

He then tried to expand this model he called He then tried to expand this model he called ““triadstriads” to the rest of the elements.” to the rest of the elements.

The concept was found to be severely limited.The concept was found to be severely limited.The next attempt was made by John The next attempt was made by John

Newlands in 1864 when he suggested that Newlands in 1864 when he suggested that elements should be arranged in “elements should be arranged in “octavesoctaves”.”.

He managed to group several elements with He managed to group several elements with similar properties but was not generally similar properties but was not generally successful.successful.

HistoryHistory

Russian scientist Dmitri Ivanovich Russian scientist Dmitri Ivanovich Mendeleeff (1834-1907) stated “Mendeleeff (1834-1907) stated “The The physical and chemical properties of the physical and chemical properties of the elements are periodic function of their elements are periodic function of their atomic weightsatomic weights.”.”

Wrote down the elements in order of Wrote down the elements in order of increasing mass.increasing mass.

Found a pattern of repeating properties.Found a pattern of repeating properties.He showed how useful the table in He showed how useful the table in

predicting the existence and properties of predicting the existence and properties of yet unknown elements.yet unknown elements.

Mendeleev’s TableMendeleev’s TableGrouped elements in columns by Grouped elements in columns by

similar propertiessimilar properties in order of in order of increasing increasing atomic mass.atomic mass.

Found some inconsistencies - felt that Found some inconsistencies - felt that the properties were more important the properties were more important than the mass, so switched order.than the mass, so switched order.

Found some gaps - must be Found some gaps - must be undiscovered elements.undiscovered elements.

Predicted their properties before they Predicted their properties before they were found. were found.

The periodic tableThe periodic tableJulius Lothar Meyer and Mendeleev was Julius Lothar Meyer and Mendeleev was

credited with conceiving the periodic tablecredited with conceiving the periodic tableElements are still grouped by properties.Elements are still grouped by properties.Similar properties are in the same column.Similar properties are in the same column.Order is in increasing atomic number.Order is in increasing atomic number.Added a column of elements Mendeleev Added a column of elements Mendeleev

didn’t know about during his time.didn’t know about during his time.The noble gases weren’t found because The noble gases weren’t found because

they didn’t react with anything.they didn’t react with anything.

Horizontal rows are called periodsHorizontal rows are called periods

There are 7 periodsThere are 7 periods1

2

3

4

5

6

7

Also called familiesAlso called families

Vertical columns are called Vertical columns are called groups.groups.

Elements are placed in columns Elements are placed in columns by similar properties.by similar properties.

4A

1A

2A 3A 5A 6A7A

8A

The elements in the A groups The elements in the A groups are called the are called the main-groupmain-group or or representativerepresentative elements elements

The Group B elementsThe Group B elements

The The group B group B are called the are called the transition elementstransition elements

These are called the inner transition elements and they belong here

2A

Group 2A are the alkaline earth metalsGroup 2A are the alkaline earth metals

1A

Group 1A are the alkali metalsGroup 1A are the alkali metalsGroup 7A is called the Halogens

7A

8A

Group 8A are the noble gases

6A

Group 6A are the chalcogens

Characteristic properties of metallic and non-metallic elements:

Metallic Elements Nonmetallic elements

Distinguishing luster (shine) Non-lustrous, various colors

Malleable and ductile (flexible) as solids

Brittle, hard or soft

Conduct heat and electricity Poor conductors

Metallic oxides are basic, ionicNonmetallic oxides are acidic, compounds

Cations in aqueous solutionAnions, oxyanions in aqueous solution

MetalloidsMetalloids

properties intermediate between properties intermediate between the metals and nonmetals. the metals and nonmetals.

ex. Silicon ex. Silicon appears lustrousappears lustrousnot malleable or ductile (it is brittle - not malleable or ductile (it is brittle -

a characteristic of some nonmetals) a characteristic of some nonmetals) it is a much poorer conductor of it is a much poorer conductor of

heat and electricity than metalsheat and electricity than metalsuseful in the semiconductor industryuseful in the semiconductor industry

AllotropyAllotropy

““allosallos” (other) & “” (other) & “tropostropos” (manner)” (manner)a property possessed by some a property possessed by some

elements that can exist in various elements that can exist in various crystalline forms or structurescrystalline forms or structures

the ability of substance to exhibit a the ability of substance to exhibit a number of different and physically number of different and physically distinct forms in its pure elemental distinct forms in its pure elemental statestate

common in non-metals and common in non-metals and metalloidsmetalloids

AllotropesAllotropes

the different forms of a substance the different forms of a substance in its pure elemental formin its pure elemental form

ex. of some allotropic elementsex. of some allotropic elementsCarbon – graphite, diamond and Carbon – graphite, diamond and

fullerenefullerenePhosphorus – red phosphorus, white Phosphorus – red phosphorus, white

phosphorus and black phosphorusphosphorus and black phosphorusOxygen – dioxygen, ozone, Oxygen – dioxygen, ozone,

tetraoxygentetraoxygen

SummaryMetals - solids (except Hg) which are

malleable, ductile (can be drawn into thin wires without breaking), and which conduct heat and electricity

Nonmetals - may be gases, liquids or solids, some are brightly colored, some are brittle solids, most are poor conductors of heat and electricity

Semimetals - properties fall between metals and nonmetals, brittle, poor conductors of heat and electricity

Types of solids

Crystalline solidsAmorphous solids

Types of compounds

ionicmolecularcovalent network

Ionic solids

High melting point and boiling point.Ionic bonds are strong. Soluble in polar solvents such as water. The ions have favorable interactions with the polar solvent and thus it takes less energy to remove them from the crystal Poor electrical conductivity. The electrons are localized around the ions, not spread out like in a metal.

Molecular compounds

Low melting and boiling points Nonconducting when pure. Molecules are uncharged and cannot carry current. Most are insoluble in water, but soluble in non-polar solvents. A few molecular substances such as ethanol dissolve in water, and a few polar ones such as HCl will ionize, but most such as oil, benzene, I2 or H2 won't.

Covalent Network

High melting point and boiling point. Covalent bonds are very strong. Insoluble in most solvents. Breaking the covalent bonds to dissolve the substance takes a lot of energy. Poor electrical conductivity. The electrons are localized in covalent bonds, not spread out like in a metal.

Introduction to Chemistry, Matter, Atomic theory, Nuclear Chemistry, The Periodic Table

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