Atomic Theory by Abhishek Jaguessar

8/4/2019 Atomic Theory by Abhishek Jaguessar

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Classification is arranging items intoClassification is arranging items intogroups or categories according to somegroups or categories according to somecriteria.criteria.The act of classifying creates a patternThe act of classifying creates a patternthat helps you recognize and understandthat helps you recognize and understandthe behavior of fish, chemicals, or anythe behavior of fish, chemicals, or anymatter in your surroundings.matter in your surroundings.


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Classifying MatterClassifying Matter


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MatterMatter is usually defined as anything that hasis usually defined as anything that hasmass and occupies space.mass and occupies space.


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Gas Liquid Solid

Total disorder Lots of empty space

Disorder Some spaceParticles closer together

Order

Particles fixedin position


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Solids, Liquids, and GasesSolids, Liquids, and GasesGasesGases have no defined shape or defined volumehave no defined shape or defined volumeLow densityLow density

LiquidsLiquids flow and can be poured from one containerflow and can be poured from one containerto anotherto another

Indefinite shape and takes on the shape of the container.Indefinite shape and takes on the shape of the container.

SolidsSolids have a definite volumehave a definite volumeHave a definite shape.Have a definite shape.


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Mixtures and Pure SubstancesMixtures and Pure SubstancesA A mixturemixture has unlike parts and a composition that has unlike parts and a composition that varies from sample to samplevaries from sample to sampleA A heterogeneous mixtureheterogeneous mixture has physically distinct has physically distinct parts with different properties.parts with different properties.A A homogeneous mixturehomogeneous mixture is the same throughout is the same throughout the samplethe samplePure substancesPure substances are substances with a fixedare substances with a fixedcompositioncomposition


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A classification scheme for matter. A classification scheme for matter.


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A A p hysical changep hysical change is a change that does not alteris a change that does not alterthe identity of the matter.the identity of the matter.A A chemical changechemical change is a change that does alter theis a change that does alter theidentity of the matter.identity of the matter.

A A com p oundcom p ound is a pure substance that can beis a pure substance that can bedecomposed by a chemical change into simplerdecomposed by a chemical change into simplersubstances with a fixed mass ratiosubstances with a fixed mass ratioAn An elementelement is a pure substance which cannot beis a pure substance which cannot bebroken down into anything simpler by eitherbroken down into anything simpler by eitherphysical or chemical means.physical or chemical means.


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Sugar ( A) is a compound that can be easilySugar ( A) is a compound that can be easilydecomposed to simpler substances by heating.decomposed to simpler substances by heating.(B) One of the simpler substances is the black(B) One of the simpler substances is the blackelement carbon, which cannot be furtherelement carbon, which cannot be furtherdecomposed by chemical or physical means.decomposed by chemical or physical means.


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Isopropyl alcohol is a

A. heterogeneous mixture

B. homogeneous mixture

C. pure substanceD. Compound

E. pure substance and compound

EXAMPLE

E


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ElementsElements


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Reconsidering the Fire ElementReconsidering the Fire ElementTheThe p hlogiston theoryp hlogiston theory viewed phlogiston as aviewed phlogiston as acomponent of all matter.component of all matter.

The burning of a material was considered to be theThe burning of a material was considered to be theescaping of phlogiston from the matter.escaping of phlogiston from the matter.If a material did not burn, it was considered toIf a material did not burn, it was considered tocontain no phlogiston.contain no phlogiston.


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The phlogiston theory.The phlogiston theory.( A) In this theory,( A) In this theory,

burning wasburning wasconsidered to be theconsidered to be theescape of phlogistonescape of phlogistoninto the air. (B ) into the air. (B ) Smelting combinedSmelting combinedphlogistonphlogiston--poor orepoor orewith phlogiston from awith phlogiston from a

fire to make a metal.fire to make a metal.(C) Metal rusting was(C) Metal rusting wasconsidered to be theconsidered to be theslow escape of slow escape of

hlo iston from ahlo iston from a


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Discovery of Modern ElementsDiscovery of Modern ElementsAntoine Lavoisier suggested that burning was Antoine Lavoisier suggested that burning wasactually a chemical combination with oxygen.actually a chemical combination with oxygen.

Lavoisier realized that there needed to be a newLavoisier realized that there needed to be a newconcept of elements, compounds, and chemicalconcept of elements, compounds, and chemicalchange.change.We now know that there are 89 naturallyWe now know that there are 89 naturally- -occurringoccurringelements and at least 23 short elements and at least 23 short- -lived and artificiallylived and artificiallyprepared.prepared.


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P riestley produced a gas (oxygen ) by using sunlight toP riestley produced a gas (oxygen ) by using sunlight toheat mercuric oxide kept in a closed container. Theheat mercuric oxide kept in a closed container. Theoxygen forced some of the mercury out of the jar as it oxygen forced some of the mercury out of the jar as it

was produced, increasing the volume about five times.was produced, increasing the volume about five times.


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Lavoisier heated a measured amount of Lavoisier heated a measured amount of

mercury to form the red oxide of mercury. Hemercury to form the red oxide of mercury. Hemeasured the amount of oxygen removed frommeasured the amount of oxygen removed fromthe jar and the amount of red oxide formed.the jar and the amount of red oxide formed.When the reaction was reversed, he found theWhen the reaction was reversed, he found the

original amounts of mercury and oxygen.original amounts of mercury and oxygen.


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Names of ElementsNames of ElementsThe first 103 elements have internationallyThe first 103 elements have internationallyaccepted names, which are derived from:accepted names, which are derived from:

The compound or substance in which the element wasThe compound or substance in which the element wasdiscovereddiscoveredAn unusual or identifying property of the element An unusual or identifying property of the element P laces, cities, and countriesP laces, cities, and countriesFamous scientistsFamous scientists

Greek mythologyGreek mythologyAstronomical objects. Astronomical objects.


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Here are some of the symbols Dalton used forHere are some of the symbols Dalton used foratoms of elements and molecules of atoms of elements and molecules of compounds. He probably used a circle for eachcompounds. He probably used a circle for eachbecause, like the ancient Greeks, he thought of because, like the ancient Greeks, he thought of atoms as tiny, round hard spheres.atoms as tiny, round hard spheres.


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The elements of aluminum, Iron, Oxygen, and SiliconThe elements of aluminum, Iron, Oxygen, and Siliconmake up about 88 percent of the earth's solid surface.make up about 88 percent of the earth's solid surface.Water on the surface and in the air as clouds and fogWater on the surface and in the air as clouds and fogis made up of hydrogen and oxygen. The air is 99is made up of hydrogen and oxygen. The air is 99percent nitrogen and oxygen. Hydrogen, oxygen, andpercent nitrogen and oxygen. Hydrogen, oxygen, andcarbon make up 97 percent of a person. Thus almost carbon make up 97 percent of a person. Thus almost

everything you see in this picture us made up of just everything you see in this picture us made up of just


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Atomic theory


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Daltons PostulatesDaltons Postulates

1 . Every element is composed of tiny particles called atoms2. All atoms of a given element are identical

1 . Atoms of different elements have different properties3. Atoms of an element are NOT changed into atoms of

another element by chemical processes1 . Matter can neither be created nor destroyed

4. Compounds are formed when atoms of more than oneelement combine


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Daltons LawsDaltons Laws

1 . The Law of Constant Composition:A ny given compound always consists of the sameatoms and the same ratio of atoms. For example, water always consists of oxygen and hydrogen atoms, and

it is always 89 percent oxygen by mass and 11 percent hydrogen by mass

2. The Law of Conservation of Mass:T he total mass of materials before and after a chemical reaction must be the same. For example, if we combine89 grams of oxygen with 11 grams of hydrogen under the appropriate conditions, 100 grams of water will be

producedno more and no less.


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Daltons LawsDaltons Laws

3. The Law of Multiple Proportions:I f two elements combine to form more than one compound,the masses of one of the elements that can combine with a givenmass of the other element are related by factors of small wholenumbers

F or example, water has an oxygen-to-hydrogen mass ratio of 7.9: 1 .Hydrogen peroxide, another compound consisting of oxygen andhydrogen, has an oxygen-to-hydrogen mass ratio of 15 .8:1 .

The ratio of these two ratios gives a small whole number.


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MODERN ATOM I C THEORY


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Chemical SymbolsChemical SymbolsThere are about a dozen common elements that There are about a dozen common elements that have s single capitalized letter for their symbolhave s single capitalized letter for their symbolThe rest, that have permanent names have twoThe rest, that have permanent names have two

letters.letters.the first is capitalized and the second is lowerthe first is capitalized and the second is lowercase.case.

Some elements have symbols from their LatinSome elements have symbols from their Latinnames.names.Ten of the elements have symbols from theirTen of the elements have symbols from theirLatin or German names.Latin or German names.


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Symbols and Atomic StructureSymbols and Atomic Structure

A A moleculemolecule is a particle that is composed of twois a particle that is composed of twoor more atoms held together by a chemical bond.or more atoms held together by a chemical bond.Isoto p esIsoto p es are atoms of an element with identicalare atoms of an element with identicalchemical properties, but different masses due tochemical properties, but different masses due toa difference in the number of neutrons.a difference in the number of neutrons.TheThe atomic massatomic mass of an element is the averageof an element is the averageof all the atomic masses of the isotopes.of all the atomic masses of the isotopes.

an isotopes contribution is determined by itsan isotopes contribution is determined by itsrelative abundance.relative abundance.


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The mass of an element is the mass of theThe mass of an element is the mass of theelement compared to an isotope of carbonelement compared to an isotope of carbonCarbon 12.Carbon 12.

Carbon 12 is assigned an atomic mass of Carbon 12 is assigned an atomic mass of

12.00 g.12.00 g.12.00 is one atomic mass unit 12.00 is one atomic mass unit The number of protons and neutrons in an atomThe number of protons and neutrons in an atomis itsis its mass numbermass number .. Atomic numbers are whole numbers Atomic numbers are whole numbersMass numbers are whole numbersMass numbers are whole numbersThe atomic mass is not a whole number.The atomic mass is not a whole number.


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HHy drogenHy drogen

1

1

Protons:1

Neutrons: 0Electrons: 1


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NaSodiumSodium

23

11

Protons: 11

Neutrons: 1 2Electrons: 11


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Rh eniumRh enium

Re1 86

75

Protons: 75

Neutrons: 111Electrons: 7 5


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Rh enium isotopeRh enium isotope

Re1 87

75

Protons: 75

Neutrons: 11 2Electrons: 7 5


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EXAM PL E

How many protons, neutrons and electrons are found in anatom of

1 3355 CsAtomic number = protons and electrons

There are55

protons and55

electronsMass number = sum of protons and neutrons

1 33 55 = 78There are 78 neutrons


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The Periodic LawThe Periodic Law


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Dmitri MedeleevDmitri Medeleev gave us a functional schemegave us a functional scheme

with which to classify elements.with which to classify elements.Mendeleev s scheme was based on chemicalMendeleev s scheme was based on chemicalproperties of the elements.properties of the elements.It was noticed that the chemical properties of It was noticed that the chemical properties of elements increased in a periodic manner.elements increased in a periodic manner.The periodicity of the elements was demonstratedThe periodicity of the elements was demonstratedby Medeleev when he used the table to predict toby Medeleev when he used the table to predict to

occurrence and chemical properties of elementsoccurrence and chemical properties of elementswhich had not yet been discovered.which had not yet been discovered.


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Mendeleev left blankMendeleev left blankspaces in his tablespaces in his tablewhen the properties of when the properties of

the elements abovethe elements aboveand below did not and below did not seem to match. Theseem to match. Theexistence of unknownexistence of unknownelements was predictedelements was predictedby Mendeleev on theby Mendeleev on thebasis of the blankbasis of the blankspaces. When thespaces. When theunknown elementsunknown elementswere discovered, it waswere discovered, it wasfound that Mendeleevfound that Mendeleevhad closely predictedhad closely predictedthe properties of thethe properties of the

elements as well aselements as well as


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The Periodic LawThe Periodic LawSimilar physical and chemical properties recurSimilar physical and chemical properties recurperiodically when the elements are listed in order of periodically when the elements are listed in order of increasing atomic number.increasing atomic number.


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The Modern Periodic TableThe Modern Periodic Table


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IntroductionIntroductionThe periodic table is made up of rows of elementsThe periodic table is made up of rows of elementsand columns.and columns.An element is identified by its chemical symbol. An element is identified by its chemical symbol.

The number above the symbol is the atomicThe number above the symbol is the atomicnumbernumberThe number below the symbol is the roundedThe number below the symbol is the roundedatomic weight of the element.atomic weight of the element.A row is called a A row is called a p eriodp eriodA column is called a A column is called a grou p grou p


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( A) P eriods of the periodic table, and (B ) ( A) P eriods of the periodic table, and (B ) groups of the periodic table.groups of the periodic table.


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Periodic PatternsPeriodic PatternsThe chemical behavior of elements is determined byThe chemical behavior of elements is determined byits electron configurationits electron configurationEnergy levels are quantized so roughly correspondEnergy levels are quantized so roughly correspondto layers of electrons around the nucleus.to layers of electrons around the nucleus.A shell is all the electrons with the same value of n. A shell is all the electrons with the same value of n.

n is a row in the periodic table.n is a row in the periodic table.

Each period begins with a new outer electron shellEach period begins with a new outer electron shell


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Each period ends with a completely filled outer shellEach period ends with a completely filled outer shell

that has the maximum number of electrons for that that has the maximum number of electrons for that shell.shell.The number identifying the A families identifies theThe number identifying the A families identifies thenumber of electrons in the outer shell, except number of electrons in the outer shell, except

heliumheliumThe outer shell electrons are responsible forThe outer shell electrons are responsible forchemical reactions.chemical reactions.Group A elements are calledGroup A elements are called re p resentativere p resentativeelementselementsGroup B elements are calledGroup B elements are called transition elementstransition elements ..


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Chemical FamiliesChemical Families

IA are calledIA are called alkali metalsalkali metals because the react withbecause the react withwater to from an alkaline solutionwater to from an alkaline solutionGroup IIA are called theGroup IIA are called the alkali earth metalsalkali earth metalsbecause they are reactive, but not as reactive asbecause they are reactive, but not as reactive asGroup IA.Group IA.

They are also soft metals like Earth.They are also soft metals like Earth.

Group V IIA are theGroup V IIA are the halogenshalogensThese need only one electron to fill their outer shellThese need only one electron to fill their outer shellThey are very reactive.They are very reactive.

Group V IIIA are theGroup V IIIA are the noble gasesnoble gases as they haveas they havecompletely filled outer shellscompletely filled outer shells

They are almost non reactive.They are almost non reactive.


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Four chemical families of theFour chemical families of theperiodic table: the alkaliperiodic table: the alkalimetals ( IA), the alkaline earthmetals ( IA), the alkaline earthmetals ( IIA) , halogens (V II) ,metals ( IIA) , halogens (V II) ,and the noble gases (V IIIA) .and the noble gases (V IIIA) .


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M etal: Elements that are usually solids at room temperature.Most elements are metals.

Non- M etal: Elements in the upper right corner of the periodicTable. Their chemical and physical properties are differentfrom metals.

Metalloid: Elements that lie on a diagonal line between theMetals and non-metals. Their chemical and physical

properties are intermediate between the two.


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When an atom or molecule gain or loses an electronWhen an atom or molecule gain or loses an electronit becomes an ion.it becomes an ion.

A A cationcation has lost an electron and therefore has ahas lost an electron and therefore has apositive chargepositive charge

An An anionanion has gained an electron and thereforehas gained an electron and thereforehas a negative charge.has a negative charge.


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Elements with 1, 2, or 3 electrons in their outerElements with 1, 2, or 3 electrons in their outershell tend toshell tend to loselose electrons to fill their outer shellelectrons to fill their outer shelland become cations.and become cations.

These are theThese are the metalsmetals which always tend to losewhich always tend to loseelectrons.electrons.

Elements with 5 to 7 electrons in their outer shellElements with 5 to 7 electrons in their outer shelltend totend to gaingain electrons to fill their outer shell andelectrons to fill their outer shell andbecome anions.become anions.

These are theThese are the nonmetalsnonmetals which always tend to gainwhich always tend to gainelectrons.electrons.

SemiconductorsSemiconductors (metalloids ) occur at the dividing(metalloids ) occur at the dividingline between metals and nonmetals.line between metals and nonmetals.


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What would the charge be on a sodium ion?

EXAM PL E

Since sodium in in Group I A it is a metal and so wouldLOS E an electron

You can tell how many would be lost by the group number Group 1 A elements lose 1 electron

So t h e c h arge would be +1

Remember an electron is negatively charged. W hen you losethem atom becomes positively charged

when you gain them it becomes negatively charged


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How would you right the symbol for the sodium CATION?

EXAM PL E

Na+1

How many outer electrons does sodium have before itloses one?

I t has 1 remember the group number!

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Atomic Theory by Abhishek Jaguessar