AtomosAtomos CLIL– Content Language Integrated

Learningg

PET - Preliminary English Testy g

Teacher: Mr Pierluigi Stroppa

Tutor: Mrs Angela Valentini

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I ti ti tI ti ti tInvestigating atomsInvestigating atoms•• You should be able to:You should be able to:

D ib th ti l th f ttD ib th ti l th f tt–– Describe the particle theory of matter Describe the particle theory of matter according to Dalton’s atom model;according to Dalton’s atom model;U th B h d l d k th th b iU th B h d l d k th th b i–– Use the Bohr model and know the three basic Use the Bohr model and know the three basic particles in the atom (proton, neutron, and particles in the atom (proton, neutron, and electron) and their charges relative masseselectron) and their charges relative masseselectron) and their charges, relative masses, electron) and their charges, relative masses, and locations. and locations. Compare the Bohr atomic model to theCompare the Bohr atomic model to the–– Compare the Bohr atomic model to the Compare the Bohr atomic model to the electron cloud modelelectron cloud model

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AtAt N t t B C t N t t B C tAtomosAtomos: Not to Be Cut: Not to Be Cut

Th Hi t f At i ThTh Hi t f At i ThThe History of Atomic TheoryThe History of Atomic Theory

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ATOMATOMATOMATOMSince the atom is too Since the atom is too

ll t bll t bsmall to be seen even small to be seen even with the most powerful with the most powerful ppmicroscopes, scientists microscopes, scientists

rely upon models torely upon models torely upon models to rely upon models to help us to understand help us to understand Even with the world’s best Even with the world’s best

microscopes we cannot clearlymicroscopes we cannot clearlyppthe atom.the atom.

microscopes we cannot clearly microscopes we cannot clearly see the structure or behavior see the structure or behavior

of the atom.of the atom.

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S i tifi M d lS i tifi M d lScientific ModelsScientific ModelsScientists create Scientists create

models to help themmodels to help themmodels to help them models to help them to visualize complex to visualize complex

properties structuresproperties structuresproperties, structures properties, structures or behaviors. Since or behaviors. Since the atom is so smallthe atom is so smallthe atom is so small, the atom is so small,

scientists must gather scientists must gather Indirect EvidenceIndirect Evidence toto This is a model of a veryThis is a model of a veryIndirect EvidenceIndirect Evidence to to

develop their models.develop their models.This is a model of a very This is a model of a very

complex molecule made of complex molecule made of many different kinds of atoms. many different kinds of atoms. Each colored ball represents anEach colored ball represents anEach colored ball represents an Each colored ball represents an

atom of a different element.atom of a different element.5

What should a Model look like?What should a Model look like?What should a Model look like?What should a Model look like?Scientific modelsScientific modelsScientific models Scientific models

may not always may not always look like the actual look like the actual object. A model is object. A model is jjan attempt to use an attempt to use familiar ideas tofamiliar ideas tofamiliar ideas to familiar ideas to

describe unfamiliar describe unfamiliar things in a visualthings in a visualthings in a visual things in a visual

way.way.This is a painting of a young woman This is a painting of a young woman b P bl Pi D it t llb P bl Pi D it t llby Pablo Picasso. Does it actually by Pablo Picasso. Does it actually

look like a young woman?look like a young woman? 6

h ll h ll Is this really an Atom?Is this really an Atom?Many of the models that you have Many of the models that you have

seen may look like the one below. It seen may look like the one below. It shows the parts and structure of theshows the parts and structure of theshows the parts and structure of the shows the parts and structure of the atom. Even though we do not know atom. Even though we do not know what an atom looks like, scientific what an atom looks like, scientific models must be based on evidencemodels must be based on evidencemodels must be based on evidence. models must be based on evidence.

The model above represents The model above represents the most modern version of the most modern version of

the atomthe atomthe atom. the atom. (Artist drawing(Artist drawing) 7

Can a Model be Changed?Can a Model be Changed?A model can be changed as new A model can be changed as new

information is collectedinformation is collectedinformation is collected. information is collected. From the early Greek concept to the From the early Greek concept to the

modern atomic theory, scientists modern atomic theory, scientists have built upon and modifiedhave built upon and modifiedhave built upon and modified have built upon and modified existing models of the atom.existing models of the atom.

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Atomic ModelsAtomic ModelsAtomic ModelsAtomic ModelsThi d l f thThi d l f th•• This model of the This model of the atom may look atom may look familiar to you. This isfamiliar to you. This isfamiliar to you. This is familiar to you. This is the Bohr model. In the Bohr model. In this model, the this model, the nucleus is orbited bynucleus is orbited bynucleus is orbited by nucleus is orbited by electrons, which are electrons, which are in different energyin different energyin different energy in different energy levels. levels.

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The Democrito’s model (400 B C )The Democrito’s model (400 B C )The Democrito s model (400 B.C.)The Democrito s model (400 B.C.)

Th iTh i•• The atomic The atomic model has model has changed changed throughout thethroughout thethroughout the throughout the centuries, centuries, starting in 400starting in 400starting in 400 starting in 400 BC, when it BC, when it looked like looked like a a billiard ball →billiard ball →billiard ball → billiard ball →

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Who are these men?Who are these men?Who are these men?Who are these men?Democrito, 400 b.C. Dalton, 1800 a.C.

In this lesson, we’ll learn about the men whose quests for knowledge about the

Democrito, 400 b.C. Dalton, 1800 a.C.

fundamental nature of the universe helped define our views.

Thomson, 1897 a.C.

Rutherford, 1911 a.C. Niels Bohr, 1913 a.C.11

DemocritusDemocritusDemocritusDemocritus•• This is the Greek This is the Greek

hil h D ithil h D it

400 BC

philosopher Democritus philosopher Democritus who began the search for a who began the search for a description of matter moredescription of matter moredescription of matter more description of matter more than than 24002400 years ago.years ago.–– He asked: Could matterHe asked: Could matterHe asked: Could matter He asked: Could matter

be divided into smaller be divided into smaller and smaller pieces and smaller pieces forever, or was there a forever, or was there a limitlimit to the number of to the number of times a piece of mattertimes a piece of mattertimes a piece of matter times a piece of matter could be could be divideddivided? ?

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AtomosAtomosAtomosAtomos

•• His theory: Matter could His theory: Matter could not be divided into not be divided into smaller and smaller smaller and smaller pieces forever, eventually pieces forever, eventually the smallest possible the smallest possible piece would be obtained.piece would be obtained.

•• This piece would be This piece would be indivisible.indivisible.

•• He named the smallest He named the smallest piece of matter “atomos,”piece of matter “atomos,”piece of matter atomos, piece of matter atomos, meaning “not to be cut.”meaning “not to be cut.” 13

AtomosAtomosAtomosAtomos

To Democritus, atoms To Democritus, atoms were were smallsmall, hard , hard particles that were all particles that were all made of the same made of the same material but were material but were differentdifferent shapes and shapes and sizes.sizes.Atoms were Atoms were infiniteinfinite in in number, always number, always moving and capable moving and capable of joining together.of joining together.

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D itD it was ignored!was ignored!Democritus Democritus was ignored!was ignored!This theory was ignored and This theory was ignored and

f f hf f h 20002000forgotten for more than forgotten for more than 2000 2000 ears!ears!years!years!

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Why?Why?Why?Why?The eminentThe eminent•• The eminent The eminent philosophers of philosophers of the time, the time, AristotleAristotle and and Plato, had a Plato, had a more respectedmore respectedmore respected, more respected, (and ultimately (and ultimately wrongwrong) theory) theory

Aristotle and Plato favored the earth, fire, airand water approach to the nature of matter.

wrongwrong) theory.) theory.

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Dalton’s ModelDalton’s ModelDalton s ModelDalton s Model

•• In the early 1800s, In the early 1800s, the English the English ggChemist John Chemist John DaltonDalton performed aperformed aDalton Dalton performed a performed a number of number of experiments thatexperiments thatexperiments that experiments that eventually led to eventually led to the acceptance of the acceptance of the idea of atoms.the idea of atoms.

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Dalton’s TheoryDalton’s TheoryDalton s TheoryDalton s Theory•• He deduced that all He deduced that all

elementselements are composed of are composed of atoms Atoms areatoms Atoms areatoms. Atoms are atoms. Atoms are indivisible and indivisible and indestructible particles.indestructible particles.pp

•• Atoms of the Atoms of the samesame element element are exactly alike.are exactly alike.

•• Atoms of Atoms of differentdifferent elements elements are are differentdifferent..

•• CompoundsCompounds are formed by are formed by the joining of atoms of two the joining of atoms of two

l tl tor more elements.or more elements.19

GlucoseGlucose

Oxygen

Carbonio

Hydrogen

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Thomson’s Plum Pudding Thomson’s Plum Pudding ModelModel

•• In In 18971897, the , the English scientistEnglish scientistEnglish scientist English scientist J.J. Thomson J.J. Thomson

id d th fi tid d th fi tprovided the first provided the first hint that an atom hint that an atom t t at a atot t at a atois made of even is made of even smallersmaller particlesparticlessmallersmaller particles.particles.

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Thomson ModelThomson ModelThomson ModelThomson ModelH dH d•• He proposed a He proposed a model of the atom model of the atom that is sometimesthat is sometimesthat is sometimes that is sometimes called the “called the “PlumPlumPuddingPudding” model” modelPuddingPudding model. model.

•• Atoms were made Atoms were made from a positivelyfrom a positivelyfrom a positively from a positively chargedcharged substancesubstancewith negativelywith negativelywith negatively with negatively charged electrons charged electrons scatteredscattered about, like about, like raisins in a pudding.raisins in a pudding.

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Thomson ModelThomson ModelThomson ModelThomson ModelTh t di dTh t di d•• Thomson studied Thomson studied the the passage passage of an of an

l t i tl t i telectric current electric current through a gas.through a gas.

•• As the current As the current passed through passed through passed t ougpassed t ougthe gas, it gave off the gas, it gave off rays ofrays of negativelynegativelyrays of rays of negatively negatively charged particles.charged particles.

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Thomson ModelThomson ModelThomson ModelThomson ModelWhere did they come

•• This surprised This surprised ThomsonThomson

they come from?

Thomson, Thomson, because the because the

t f tht f thatoms of the gas atoms of the gas were uncharged. were uncharged. e e u c a gede e u c a gedWhere had the Where had the negati e chargesnegati e chargesnegative charges negative charges come from?come from?

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Thomson concluded that the negative charges came from withinthe atom.

A particle smaller than an atom had to exist.

The atom was divisible!

Thomson called the negatively g ycharged “corpuscles,” today known as electrons.

Since the gas was known to be neutral, having no charge, he reasoned that there must bereasoned that there must be positively charged particles in the atom.

But he could never find them. 25

Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment

•• In 1908, the In 1908, the English physicist English physicist g p yg p yErnest Rutherford Ernest Rutherford was hard at workwas hard at workwas hard at work was hard at work on an experiment on an experiment that seemed tothat seemed tothat seemed to that seemed to have little to do have little to do with unraveling the with unraveling the mysteries of the mysteries of the yyatomic structure.atomic structure. 26

Rutherford’s experimentRutherford’s experimentRutherford s experimentRutherford s experiment•• Rutherford’s experiment Involved Rutherford’s experiment Involved

firing a stream of tinyfiring a stream of tiny positivelypositivelyfiring a stream of tiny firing a stream of tiny positively positively chargedcharged particles at a thin sheet of particles at a thin sheet of

ld f illd f il (2000 t thi k)(2000 t thi k)gold foilgold foil (2000 atoms thick)(2000 atoms thick)

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Rutherford’s experimentRutherford’s experimentRutherford s experimentRutherford s experimentM tM t f th iti lf th iti l–– MostMost of the positively of the positively charged “bullets” passed charged “bullets” passed right through the goldright through the goldright through the gold right through the gold atoms in the sheet of atoms in the sheet of gold gold foilfoil without changing without changing

t llt llcourse at all.course at all.–– SomeSome of the positively of the positively

charged “bullets ”charged “bullets ”charged bullets, charged bullets, however, did bounce however, did bounce away from the gold sheet away from the gold sheet y gy gas if they had hit as if they had hit something something solidsolid. He knew . He knew that positive chargesthat positive charges repelrepelthat positive charges that positive charges repelrepelpositive charges.positive charges. 28

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The nucleusThe nucleusThe nucleusThe nucleusThi ld l th t th ld t i thThi ld l th t th ld t i th•• This could only mean that the gold atoms in the This could only mean that the gold atoms in the sheet were mostly sheet were mostly open spaceopen space. Atoms were . Atoms were notnota pudding filled with a positively chargeda pudding filled with a positively chargeda pudding filled with a positively charged a pudding filled with a positively charged material.material.

•• Rutherford concluded that an atom had aRutherford concluded that an atom had a smallsmall•• Rutherford concluded that an atom had a Rutherford concluded that an atom had a small, small, dense, positively charged centerdense, positively charged center that that repelledrepelledhis positively charged “bullets ”his positively charged “bullets ”his positively charged bullets.his positively charged bullets.

•• He called the center of the atom the “He called the center of the atom the “nucleusnucleus””•• The nucleus isThe nucleus is tinytiny compared to the atom as acompared to the atom as a•• The nucleus is The nucleus is tiny tiny compared to the atom as a compared to the atom as a

whole. whole.

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RutherfordRutherfordRutherfordRutherford

•• Rutherford reasoned Rutherford reasoned that all of an atom’s that all of an atom’s positively charged positively charged particles were particles were containedcontained in the in the nucleus. The nucleus. The negatively charged negatively charged particles were particles were scatteredscattered outside the outside the nucleus around the nucleus around the atom’s atom’s edgeedge..

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Bohr ModelBohr ModelBohr ModelBohr Model

•• In 1913, the Danish In 1913, the Danish scientistscientist NielsNiels BohrBohrscientist scientist NielsNiels Bohr Bohr proposed an proposed an p pp pimprovement. In his improvement. In his model he placedmodel he placedmodel, he placed model, he placed each electron in a each electron in a specificspecific energy energy levellevellevel.level.

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Bohr ModelBohr ModelBohr ModelBohr Model•• According to According to gg

Bohr’s atomic Bohr’s atomic model, electrons model, electrons ,,move in definite move in definite orbitsorbits around thearound theorbitsorbits around the around the nucleus, much like nucleus, much like planets circle theplanets circle theplanets circle the planets circle the sun. These orbits, sun. These orbits, or energyor energy levelslevelsor energy or energy levelslevels, , are located at are located at certaincertain distancesdistancescertaincertain distances distances from the nucleus.from the nucleus. 33

Wave Model

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The Wave ModelThe Wave ModelThe Wave ModelThe Wave ModelT d ’ t iT d ’ t i•• Today’s atomic Today’s atomic model is based on model is based on the principles ofthe principles ofthe principles of the principles of wavewave mechanicsmechanics..

•• According to theAccording to the•• According to the According to the theory of wave theory of wave mechanicsmechanicsmechanics, mechanics, electrons electrons do not do not movemove about anabout anmovemove about an about an atom in a atom in a definite definite path,path, like the like the ppplanets around the planets around the sun.sun. 35

The Wave ModelThe Wave ModelThe Wave ModelThe Wave ModelI f t it iI f t it i i ibli ibl t d t i th tt d t i th t•• In fact, it is In fact, it is impossibleimpossible to determine the exact to determine the exact location of an electron. The location of an electron. The probableprobable location of location of an electron is based on how muchan electron is based on how much energyenergy thethean electron is based on how much an electron is based on how much energyenergy the the electron has.electron has.

•• According to the modern atomic model at atomAccording to the modern atomic model at atom•• According to the modern atomic model, at atom According to the modern atomic model, at atom has a has a small positively charged nucleussmall positively charged nucleussurrounded by a large region in which there aresurrounded by a large region in which there aresurrounded by a large region in which there are surrounded by a large region in which there are enough electrons to make an atom neutral.enough electrons to make an atom neutral.

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Electron Cloud:Electron Cloud:Electron Cloud:Electron Cloud:A space in whichA space in which•• A space in which A space in which electrons are likely to be electrons are likely to be found.found.

•• Electrons Electrons whirlwhirl about the about the nucleus billions of times nucleus billions of times in one secondin one second

•• They are not moving They are not moving around in around in randomrandompatternspatternspatterns.patterns.

•• Location of electrons Location of electrons depends upon how much depends upon how much

th l t hth l t henergyenergy the electron has.the electron has.

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Electron Cloud:Electron Cloud:Electron Cloud:Electron Cloud:

•• Depending on their energy they are locked into a Depending on their energy they are locked into a certain area in the cloudcertain area in the cloudcertain area in the cloud.certain area in the cloud.

•• Electrons with the Electrons with the lowestlowest energy are found in energy are found in the energy levelthe energy level closestclosest to the nucleusto the nucleusthe energy level the energy level closestclosest to the nucleusto the nucleus

•• Electrons with the Electrons with the highesthighest energy are found energy are found in the in the outermostoutermost energy levels, farther from energy levels, farther from the nucleus.the nucleus.

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IndivisibleIndivisible ElectronElectron NucleusNucleus OrbitOrbit Electron Electron CloudCloud

GreekGreek XX

DaltonDalton XXDaltonDalton XX

ThomsonThomson XX

RutherfordRutherford XX XX

BohrBohr XX XX XXBohrBohr XX XX XX

WaveWave XX XX XX

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