present at a ion 01
TRANSCRIPT
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Well comeThis PowerPoint presentation hasbeen made by Kabita The group
leader NishaNidhi NehaKavita
Well comeThis PowerPoint presentation hasbeen made by Kabita The group
leader NishaNidhi NehaKavita
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Structure of AtomStructure of Atom
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• Atoms and molecules are the building
blocks of matter.
• The existence of different kinds of matter
around us is due to different types of atoms
are the smallest particle of an element.• to different types of atoms and molecules
present in them.
• The atoms are divisible and they do have
an inner structure.
• Atoms have smaller particles in them which
are called subatomic particles.
• Atoms and molecules are the building
blocks of matter.
• The existence of different kinds of matter
around us is due to different types of atoms
are the smallest particle of an element.• to different types of atoms and molecules
present in them.
• The atoms are divisible and they do have
an inner structure.
• Atoms have smaller particles in them which
are called subatomic particles.
ATOMATOM
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DALTON’S ATOMIC THEORYDALTON’S ATOMIC THEORY
According to “DALTON’S ATOMIC THEORY’’ ,all
matter , whether an element , a compound or amixture is composed of small particles called atoms ,
the postulates of this theory may be stated as
follows:
• All matter is made of very tiny particles called atoms.
• Atoms are indivisible particles , which cannot becreated nor be destroyed in a chemical reaction.
• Atoms of a given element are identical in mass and
chemical reaction.
• Atoms of different elements have different masses
and chemical properties.
• Atoms combine in the ratio of small whole numbers
to form compounds.
• The relative number and kinds of atoms are
Constant in a given compound.
According to “DALTON’S ATOMIC THEORY’’ ,all
matter , whether an element , a compound or amixture is composed of small particles called atoms ,
the postulates of this theory may be stated as
follows:
• All matter is made of very tiny particles called atoms.
• Atoms are indivisible particles , which cannot becreated nor be destroyed in a chemical reaction.
• Atoms of a given element are identical in mass and
chemical reaction.
• Atoms of different elements have different masses
and chemical properties.
• Atoms combine in the ratio of small whole numbers
to form compounds.
• The relative number and kinds of atoms are
Constant in a given compound.
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Subatomic ParticlesSubatomic ParticlesSubatomic ParticlesSubatomic Particles
3 types:3 typ
es:
• Electron:Electron: negatively
charged• Proton:Proton: positively
charged
• Neutron:Neutron: neutralparticles
3 typ
es:3 typ
es:
• Electron:Electron: negatively
charged• Proton:Proton: positively
charged
• Neutron:Neutron: neutralparticles
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Subatomic ParticlesSubatomic Particles
ParticleParticle ChargeCharge Mass (g)Mass (g) LocationLocation
ElectronElectron
(e(e--)) -1-1 9.11 x 109.11 x 10-28-28 ElectronElectron
cloudcloud
ProtonProton
(p(p++)) +1+1
1010-24-24
1.67 x1.67 x NucleusNucleus
NeutronNeutron
(n(noo)) 00 1.67 x 101.67 x 10-24-24 NucleusNucleus
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The number of subatomicparticles in the following:The number of subatomicparticles in the following:
.Cl has a mass # of 35 and an atomic #of 17– p+ = 17, no = 18, e- = 17
• K has a mass # of 39 and an atomic #of 19– P+ = 19, no = 20 e- = 19.
.Cl has a mass # of 35 and an atomic #of 17– p+ = 17, no = 18, e- = 17
• K has a mass # of 39 and an atomic #of 19– P+ = 19, no = 20 e- = 19.
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ELECTRONS ELECTRONS ELECTRONS ELECTRONS
• The existence of electrons in anatom was shown by
J.J.Thomson in 1897.
• Thomson was englishphysicsts.
• The existence of electrons in anatom was shown by
J.J.Thomson in 1897.
• Thomson was englishphysicsts.
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DISCOVERY OF ELECTRONS DISCOVERY OF ELECTRONS DISCOVERY OF ELECTRONS DISCOVERY OF ELECTRONS
Since all the gases from cathode rays, it wasSince all the gases from cathode rays, it was
concluded that all the atoms containconcluded that all the atoms contain
negatively charged particles called electron.negatively charged particles called electron.
Fast moving electron from cathode rays.Fast moving electron from cathode rays.
The electron is a negatively chargedThe electron is a negatively charged
particles found in the atoms of all theparticles found in the atoms of all the
elements.elements.The electrons are located outside theThe electrons are located outside the
nucleus in an atom.nucleus in an atom.
Cathode rays consists of small, negativelyCathode rays consists of small, negatively
charged particles called electrons .charged particles called electrons .
The existence of electrons in an atom wasThe existence of electrons in an atom wasshown by J.H. Thomson in 1897.shown by J.H. Thomson in 1897.
Since all the gases from cathode rays, it wasSince all the gases from cathode rays, it was
concluded that all the atoms containconcluded that all the atoms contain
negatively charged particles called electron.negatively charged particles called electron.
Fast moving electron from cathode rays.Fast moving electron from cathode rays.
The electron is a negatively chargedThe electron is a negatively charged
particles found in the atoms of all theparticles found in the atoms of all the
elements.elements.The electrons are located outside theThe electrons are located outside the
nucleus in an atom.nucleus in an atom.
Cathode rays consists of small, negativelyCathode rays consists of small, negatively
charged particles called electrons .charged particles called electrons .
The existence of electrons in an atom wasThe existence of electrons in an atom wasshown by J.H. Thomson in 1897.shown by J.H. Thomson in 1897.
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DISCOVERY OF PROTONDISCOVERY OF PROTON• Protons are the positively charged
particles the existence of proton in the
atoms was shown by E.Goldstein.• When Goldstein passed electricity at high
voltage through a gas at very low
pressure taken in a discharge tube,
stream of heavy particles were given out
by the anode.• These streams of particles are called
anode rays.
• Anode rays consists of positively charged
particles.
• The anode rays obtained from hydrogen
gas consists of protons.
• These fast moving proton form the anode
rays, The proton is positively charged
particle found in the atoms of all theelements.
• Protons are the positively charged
particles the existence of proton in the
atoms was shown by E.Goldstein.• When Goldstein passed electricity at high
voltage through a gas at very low
pressure taken in a discharge tube,
stream of heavy particles were given out
by the anode.• These streams of particles are called
anode rays.
• Anode rays consists of positively charged
particles.
• The anode rays obtained from hydrogen
gas consists of protons.
• These fast moving proton form the anode
rays, The proton is positively charged
particle found in the atoms of all theelements.
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DISCOVERY OF PROTONDISCOVERY OF PROTON
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CHARACTERISTICS OF AN
ELECTRON
CHARACTERISTICS OF AN
ELECTRONMass of an electronMass of an electron
• The relative mass of an electron isThe relative mass of an electron is
1/1840u.the absolute mass of an1/1840u.the absolute mass of an
electron iselectron is 9.11 x 109.11 x 10-28-28 gram.gram.
Charge of an electronCharge of an electron
• The absolute charge of an electron is1.67 x 10The absolute charge of an electron is1.67 x 10-19-19
coulomb of negative charge . The relative chargecoulomb of negative charge . The relative chargeof an electron is -1[minus one].of an electron is -1[minus one].
Mass of an electronMass of an electron
• The relative mass of an electron isThe relative mass of an electron is
1/1840u.the absolute mass of an1/1840u.the absolute mass of an
electron iselectron is 9.11 x 109.11 x 10-28-28 gram.gram.
Charge of an electronCharge of an electron
• The absolute charge of an electron is1.67 x 10The absolute charge of an electron is1.67 x 10-19-19
coulomb of negative charge . The relative chargecoulomb of negative charge . The relative chargeof an electron is -1[minus one].of an electron is -1[minus one].
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NEUTRONNEUTRON
• Neutron was
discovered by thephysician sir
Chadwick in 1932.
• Neutron was
discovered by thephysician sir
Chadwick in 1932.
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DISCOVERY OF NEUTRONDISCOVERY OF NEUTRON
• The Neutron is a neutral particle found in the nucleus of anatom.
• The sub atomic particle not present in hydrogen atom is
neutron.
• The sub atomic particles not present in the hydrogen is neutron.• This problem was solve by the discovery of another sub atomic
particle by Chadwick in 1932.
• The neutron is a neutral particle found in the nucleus of an
atom.• Thus the sub atomic particles not present in a hydrogen atom is
neutron.
• An hydrogen atom contain only one proton and one electron.
• A neutron is represented by the symbol N.
• The Neutron is a neutral particle found in the nucleus of anatom.
• The sub atomic particle not present in hydrogen atom is
neutron.
• The sub atomic particles not present in the hydrogen is neutron.• This problem was solve by the discovery of another sub atomic
particle by Chadwick in 1932.
• The neutron is a neutral particle found in the nucleus of an
atom.• Thus the sub atomic particles not present in a hydrogen atom is
neutron.
• An hydrogen atom contain only one proton and one electron.
• A neutron is represented by the symbol N.
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THOMSON’S MODEL OF THE ATOMTHOMSON’S MODEL OF THE ATOMTHOMSON’S MODEL OF THE ATOMTHOMSON’S MODEL OF THE ATOM
When J.J. Thomson proposed his model of When J.J. Thomson proposed his model of thethe
atom in 1930, then only electron andatom in 1930, then only electron andprotonsprotons
known to be present in the atom. Accordingknown to be present in the atom. Accordingtoto
Thomson model of the atom:Thomson model of the atom:
1.1. An atom consists of sphere of positiveAn atom consists of sphere of positivecharged with negatively chargedcharged with negatively chargedelectron embedded in it.electron embedded in it.
2.2. The positive and negative charged inThe positive and negative charged inan atom are equal in magnitude, due toan atom are equal in magnitude, due towhich an atom is electrically neutron itwhich an atom is electrically neutron it
has not overall positive or negativehas not overall positive or negativecharged.charged.
When J.J. Thomson proposed his model of When J.J. Thomson proposed his model of thethe
atom in 1930, then only electron andatom in 1930, then only electron andprotonsprotons
known to be present in the atom. Accordingknown to be present in the atom. Accordingtoto
Thomson model of the atom:Thomson model of the atom:
1.1. An atom consists of sphere of positiveAn atom consists of sphere of positivecharged with negatively chargedcharged with negatively charged
electron embedded in it.electron embedded in it.
2.2. The positive and negative charged inThe positive and negative charged inan atom are equal in magnitude, due toan atom are equal in magnitude, due towhich an atom is electrically neutron itwhich an atom is electrically neutron it
has not overall positive or negativehas not overall positive or negativecharged.charged.
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Thomson’s Atomic ModelThomson’s Atomic Model
Thomson believed that
the electrons were like
plums embedded in a
positively charged
“pudding,” thus it was
called the “plum pudding”model.
J. J. ThomsonJ. J. Thomson
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Thomson’s Atomic ModelThomson’s Atomic Model
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Gold foilGold foil
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Gold foilGold foil
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Gold foilGold foil
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RUTHERFORD’S MODEL OF THERUTHERFORD’S MODEL OF THEATOMATOM
RUTHERFORD’S MODEL OF THERUTHERFORD’S MODEL OF THEATOMATOM
1.1. An atom consists of a positively charged,An atom consists of a positively charged,dense and very small nucleus containing ondense and very small nucleus containing onthe proton and neutron. Almost the entire massthe proton and neutron. Almost the entire massof an atom is concentrated in the nucleus.of an atom is concentrated in the nucleus.
2.2. The nucleus is surrounded by negativelyThe nucleus is surrounded by negativelycharged electrons. The electron are revolvingcharged electrons. The electron are revolvinground the nucleus in circular paths at very highround the nucleus in circular paths at very highspeed. The circular path of the electron arespeed. The circular path of the electron arecalled orbits.called orbits.
3.3. The electrostatic attraction between theThe electrostatic attraction between thepositively charged nucleus and negativelypositively charged nucleus and negatively
charged electron hold the atom together.charged electron hold the atom together.4.4. An atom is electrical neutral. This is becauseAn atom is electrical neutral. This is because
the number of protons an electrons in an atomthe number of protons an electrons in an atomis equal.is equal.
5.5. Most of the atom is empty space.Most of the atom is empty space.
1.1. An atom consists of a positively charged,An atom consists of a positively charged,dense and very small nucleus containing ondense and very small nucleus containing onthe proton and neutron. Almost the entire massthe proton and neutron. Almost the entire massof an atom is concentrated in the nucleus.of an atom is concentrated in the nucleus.
2.2. The nucleus is surrounded by negativelyThe nucleus is surrounded by negativelycharged electrons. The electron are revolvingcharged electrons. The electron are revolvinground the nucleus in circular paths at very highround the nucleus in circular paths at very highspeed. The circular path of the electron arespeed. The circular path of the electron arecalled orbits.called orbits.
3.3. The electrostatic attraction between theThe electrostatic attraction between thepositively charged nucleus and negativelypositively charged nucleus and negatively
charged electron hold the atom together.charged electron hold the atom together.4.4. An atom is electrical neutral. This is becauseAn atom is electrical neutral. This is because
the number of protons an electrons in an atomthe number of protons an electrons in an atomis equal.is equal.
5.5. Most of the atom is empty space.Most of the atom is empty space.
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RUTHERFORD’S MODEL OF THERUTHERFORD’S MODEL OF THEATOMATOM
RUTHERFORD’S MODEL OF THERUTHERFORD’S MODEL OF THEATOMATOM
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• Based on his experimental evidence:
– The atom is mostly empty space
– All the positive charge, and almost all
the mass is concentrated in a small areain the center. He called this a “nucleus”
– The nucleus is comosed of protons andneutrons (they make the nucleus!)
–The electrons distributed around thenucleus, and occupy most of the volume
– His model was called a “nuclear model”
• Based on his experimental evidence:
– The atom is mostly empty space
– All the positive charge, and almost all
the mass is concentrated in a small areain the center. He called this a “nucleus”
– The nucleus is comosed of protons andneutrons (they make the nucleus!)
– The electrons distributed around thenucleus, and occupy most of the volume
– His model was called a “nuclear model”
• RUTHERFORD’S ALPHA PARTICLESSCATTERING EXPERICEMENT SHOWS THE
PRESENTS OF NUCLEUS IN THE ATOM
• RUTHERFORD’S ALPHA PARTICLESSCATTERING EXPERICEMENT SHOWS THE
PRESENTS OF NUCLEUS IN THE ATOM
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SCATTERING OF ALPHA PARTICLES BY A GOLD
FOIL
SCATTERING OF ALPHA PARTICLES BY A GOLD
FOIL
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Gold foilGold foil
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Expectations versus RealityExpectations versus Reality
Ernest Rutherford’sErnest Rutherford’s
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Ernest Rutherford s
Gold Foil Experiment - 1911
Ernest Rutherford s
Gold Foil Experiment - 1911
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THE ATOM
THE ATOM
A Major draw back of Rutherford’s model of the atom isA Major draw back of Rutherford’s model of the atom is
that he doesn’t explain the stability of the atom.that he doesn’t explain the stability of the atom.
According to the electromagnetic theory of physics, if According to the electromagnetic theory of physics, if
charged particle undergoes accelerated motion then itcharged particle undergoes accelerated motion then it
must radiate energy continuously. Negatively chargedmust radiate energy continuously. Negatively charged
electrons revolving around the nucleus with acceleratedelectrons revolving around the nucleus with acceleratedmotion, will loss the energy continuously by radiation.motion, will loss the energy continuously by radiation.
Thus, the energy of revolving electron will decreasedThus, the energy of revolving electron will decreased
gradually and there speed will also go on decreasing.gradually and there speed will also go on decreasing.
The electrons will then the attracted more strongly by theThe electrons will then the attracted more strongly by theoppositely charged nucleus due to which they will comeoppositely charged nucleus due to which they will come
more and more close to the nucleus. An ultimately themore and more close to the nucleus. An ultimately the
electron should fall into the nucleus by taking a spiralelectron should fall into the nucleus by taking a spiral
part. This should make the atom very unstable and hencepart. This should make the atom very unstable and hence
the atom should collapse.the atom should collapse.
Th R th f d At i M d lTh R th f d At i M d l
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The Rutherford Atomic ModelThe Rutherford Atomic Model• Based on his experimental evidence:
–The atom is mostly empty space –All the positive charge, and almost all
the mass is concentrated in a small area
in the center. He called this a “nucleus” –The nucleus is composed of protons
and neutrons (they make the nucleus!)
–The electrons distributed around thenucleus, and occupy most of the volume
–His model was called a “nuclear model”
• Based on his experimental evidence:
–The atom is mostly empty space –All the positive charge, and almost all
the mass is concentrated in a small area
in the center. He called this a “nucleus” –The nucleus is composed of protons
and neutrons (they make the nucleus!)
–The electrons distributed around thenucleus, and occupy most of the volume
–His model was called a “nuclear model”
Th R th f d At i M d lTh R th f d At i M d l
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The Rutherford Atomic ModelThe Rutherford Atomic Model• Based on his experimental evidence:
–The atom is mostly empty space –All the positive charge, and almost all
the mass is concentrated in a small area
in the center. He called this a “nucleus” –The nucleus is composed of protons
and neutrons (they make the nucleus!)
–The electrons distributed around thenucleus, and occupy most of the volume
–His model was called a “nuclear model”
• Based on his experimental evidence:
–The atom is mostly empty space –All the positive charge, and almost all
the mass is concentrated in a small area
in the center. He called this a “nucleus” –The nucleus is composed of protons
and neutrons (they make the nucleus!)
–The electrons distributed around thenucleus, and occupy most of the volume
–His model was called a “nuclear model”
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Rutherford’s problem:Rutherford’s problem:In the following pictures, there is a targetIn the following pictures, there is a target
hidden by a cloud. To figure out the shape of hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloudthe target, we shot some beams into the cloud
and recorded where the beams came out. Canand recorded where the beams came out. Can
you figure out the shape of the target?you figure out the shape of the target?
TargetTarget
#1#1
TargetTarget
#2#2
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The Answers:The Answers:
Target #1Target #1 Target #2Target #2
NEILS BOHR MODEL OF THE ATOMNEILS BOHR MODEL OF THE ATOM
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NEILS BOHR MODEL OF THE ATOMNEILS BOHR MODEL OF THE ATOM
1. An atom is made of three particles: Electrons, Protons andNeutrons.
Due to the presences of equal number of negative electrons andpositive protons the atom on the hold is electrically neutral.
2. The proton and neutron are located in a small nucleus at the center of the atom. Due to the presences of proton, Nucleus is positively
charged.3. The electron revolved round the nucleus in a fix circular paths
called energy level or shells.
4. The energy level are represented by the number 1,2,3,4,5 and 6 bythe later K,L,M,O.
5. There is a limit to the number of electron which is energy level canhold for example the first energy level K. Shell can hold amaximum of two electron second level can hold a eight electron.The third energy level can hold 18 electron and forth energy levelcan hold 32 electron.
1. An atom is made of three particles: Electrons, Protons andNeutrons.
Due to the presences of equal number of negative electrons andpositive protons the atom on the hold is electrically neutral.
2. The proton and neutron are located in a small nucleus at the center of the atom. Due to the presences of proton, Nucleus is positively
charged.3. The electron revolved round the nucleus in a fix circular pathscalled energy level or shells.
4. The energy level are represented by the number 1,2,3,4,5 and 6 bythe later K,L,M,O.
5. There is a limit to the number of electron which is energy level canhold for example the first energy level K. Shell can hold amaximum of two electron second level can hold a eight electron.The third energy level can hold 18 electron and forth energy levelcan hold 32 electron.
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How exactly are the particles
arranged?
How exactly are the particles
arranged?
• Bohr Model of the atom:Reviewers think this could lead to misconceptions!
• Bohr Model of the atom:Reviewers think this could lead to misconceptions!
All of theAll of theprotonsprotons
and theand theneutronsneutrons
The 1The 1stst ringringcan hold upcan hold up
to 2 eto 2 e--
The 2The 2ndnd ringringcan hold upcan hold up
to 8 eto 8 e--
The 3The 3rdrd ring canring canhold uphold up
to 18 eto 18 e--
The 4The 4thth ring andring andany after canany after canhold up to 32 ehold up to 32 e--
ATOMIC NUMBERATOMIC NUMBER
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ATOMIC NUMBERATOMIC NUMBER
The number of proton in one atom of an elementis known as atomic number of the element.
Atomic number of an element = Number of proton
in one element of an atom.The atomic number is denoted by later Z. All the
atom of the same element have the same
number of proton in the nuclei, and hence they have the
same atomic number.
The atomic number of an element = Number of
The number of proton in one atom of an elementis known as atomic number of the element.
Atomic number of an element = Number of proton
in one element of an atom.The atomic number is denoted by later Z. All the
atom of the same element have the same
number of proton in the nuclei, and hence they have the
same atomic number.
The atomic number of an element = Number of
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Atomic Number Atomic Number
Atomic number (Z) of an element isAtomic number (Z) of an element is
the number of protons in the nucleusthe number of protons in the nucleus
of each atom of that element.of each atom of that element.
ElementElement # of protons# of protons Atomic # (Z)Atomic # (Z)
CarbonCarbon 66 66
PhosphorusPhosphorus 1515 1515
GoldGold 7979 7979
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Atomic Number Atomic Number
•Atoms are composed of
identical protons, neutrons, and electrons
– How then are atoms of one element
different from another element?• Elements are different because they
contain different numbers of PROTONS
• The “atomic number ” of an element isthe number of protons in the nucleus
• # protons in an atom = # electrons
• Atoms are composed of identical
protons, neutrons, and electrons
– How then are atoms of one element
different from another element?• Elements are different because they
contain different numbers of PROTONS
• The “atomic number ” of an element isthe number of protons in the nucleus
• # protons in an atom = # electrons
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Atomic MassAtomic Mass
Total number of proton and neutron present in
one atom of an element is known as its mass
number.
Mass number = Number of proton + Number of Neutron.
The mass number of an element is denoted by
latter A. Mass number = atomic mass
Total number of proton and neutron present in
one atom of an element is known as its mass
number.
Mass number = Number of proton + Number of Neutron.
The mass number of an element is denoted by
latter A. Mass number = atomic mass
Atomic MassesAtomic Masses
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Atomic MassesAtomic Masses
IsotopeIsotope SymbolSymbol Composition of Composition of the nucleusthe nucleus
% in nature% in nature
Carbon-12Carbon-12 1212 CC 6 protons6 protons
6 neutrons6 neutrons
98.89%98.89%
Carbon-13Carbon-13 1313 CC 6 protons6 protons
7 neutrons7 neutrons
1.11%1.11%
Carbon-14Carbon-14 1414 CC 6 protons6 protons8 neutrons8 neutrons
<0.01%<0.01%
Atomic mass is the average of all theAtomic mass is the average of all the
naturally occurring isotopes of thatnaturally occurring isotopes of that
element.element.
Carbon = 12.011Carbon = 12.011
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• Mass number: the number of protons
and neutrons in the nucleus– Ex: hydrogen can have a mass of 3.
Since it has 1 proton it must have 2
neutrons
– # of neutrons = mass # - atomic #
• Mass number: the number of protons
and neutrons in the nucleus– Ex: hydrogen can have a mass of 3.
Since it has 1 proton it must have 2
neutrons
– # of neutrons = mass # - atomic #
How do we know the number of
subatomic particles in an atom?
How do we know the number of
subatomic particles in an atom?
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Measuring Atomic MassMeasuring Atomic Mass
• Instead of grams, the unit we useis the Atomic Mass Unit (amu)
• It is defined as one-twelfth themass of a carbon-12 atom. – Carbon-12 chosen because of its isotope purity.
• Each isotope has its own atomicmass, thus we determine theaverage from percent abundance.
• Instead of grams, the unit we useis the Atomic Mass Unit (amu)
• It is defined as one-twelfth themass of a carbon-12 atom. – Carbon-12 chosen because of its isotope purity.
• Each isotope has its own atomicmass, thus we determine theaverage from percent abundance.
Mass NumberMass Number
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Mass Number Mass Number
Mass number is the number of protonsMass number is the number of protons
and neutrons in the nucleus of anand neutrons in the nucleus of an
isotope:isotope: Mass # = pMass # = p++ + n+ n00
NuclideNuclide pp++ nn00 ee-- Mass #Mass #
OxygenOxygen -- 1010
-- 3333 4242
-- 3131 1515
88 88 18181818
ArsenicArsenic 7575 3333 7575
PhosphorusPhosphorus 1515 31311616
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Complete SymbolsComplete Symbols
• Contain the symbol of the element,the mass number and the atomic
number.
• Contain the symbol of the element,the mass number and the atomic
number.
XX
MassMassnumber number
AtomicAtomic
number number SubscriptSubscript →→
Superscript →Superscript →
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SymbolsSymbols
s Find each of these:Find each of these:a)a) number of protonsnumber of protons
b)b) number of number of neutronsneutrons
c)c) number of number of
electronselectronsd)d) Atomic number Atomic number
e)e) Mass Number Mass Number
Br Br 8080
3535
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SymbolsSymbols
s If an element has an atomicIf an element has an atomicnumber of 34 and a massnumber of 34 and a mass
number of 78, what is the:number of 78, what is the:
a)a) number of protonsnumber of protons
b)b) number of neutronsnumber of neutrons
c)c) number of electronsnumber of electrons
d)d) complete symbolcomplete symbol
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IsotopesIsotopes
• Dalton was wrong about allelements of the same typebeing identical
• Atoms of the same element can have different numbers of
neutrons.• Thus, different mass numbers.
• These are called isotopes.
• Dalton was wrong about allelements of the same typebeing identical
• Atoms of the same element can have different numbers of
neutrons.• Thus, different mass numbers.
• These are called isotopes.
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IsotopesIsotopes
• Frederick Soddy (1877-1956)
proposed the idea of isotopes in 1912
• Isotopes are atoms of the same elementhaving different masses, due to varying
numbers of neutrons.
• Soddy won the Nobel Prize in Chemistry in
1921 for his work with isotopes and
radioactive materials.
• Frederick Soddy (1877-1956)
proposed the idea of isotopes in 1912
• Isotopes are atoms of the same element having different masses, due to varying
numbers of neutrons.
• Soddy won the Nobel Prize in Chemistry in
1921 for his work with isotopes and
radioactive materials.
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Naming IsotopesNaming Isotopes
• We can also put the massnumber after the name of the
element: –carbon-12
–carbon-14 –uranium-235
• We can also put the massnumber after the name of the
element: –carbon-12
–carbon-14 –uranium-235
I tI t t f tht f th l tl t h ih i
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IsotopesIsotopes are atoms of theare atoms of the same elementsame element havinghaving
different massesdifferent masses, due to varying numbers of , due to varying numbers of
neutrons.neutrons.IsotopeIsotope ProtonsProtons ElectronsElectrons NeutronsNeutrons NucleusNucleus
Hydrogen–1Hydrogen–1
(protium)(protium) 11 11 00
Hydrogen-2Hydrogen-2
(deuterium)(deuterium) 11 11 11
Hydrogen-3Hydrogen-3(tritium)(tritium)
11 11 22
II t
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IsotopesIsotopesElementsElements
occur inoccur innature asnature as
mixturesmixtures of of
isotopes.isotopes.
Isotopes areIsotopes are
atoms of theatoms of the
same elementsame elementthat differ inthat differ in
thethe number of number of
neutrons.neutrons.
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1922 Niels Bohr 1922 Niels Bohr
• Electrons closer to the nucleus have lower energy and are more stable due to strong
electrostatic attraction with the nucleus.
• The letter “n” is used to designate energy
levels (orbits), with lower whole number values of n representing lower energy orbits
closer to the nucleus.
• The key to Bohr’s Quantum Model was that
electrons are restricted to certain“allowed” energy levels in atoms.
• Whereas Rutherford suggested electrons
orbit the nucleus, Bohr’s model required that
they occupy only certain orbits!
• Electrons closer to the nucleus have lower energy and are more stable due to strong
electrostatic attraction with the nucleus.
• The letter “n” is used to designate energy
levels (orbits), with lower whole number values of n representing lower energy orbits
closer to the nucleus.
• The key to Bohr’s Quantum Model was that
electrons are restricted to certain“allowed” energy levels in atoms.
• Whereas Rutherford suggested electrons
orbit the nucleus, Bohr’s model required that
they occupy only certain orbits!
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Representative, Transition, & Rare Earth
Elements
Representative, Transition, & Rare Earth
Elements
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Cathode Ray TubesCathode Ray Tubes
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2
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Thank
You
Thank
You• For your cooperation with us during
our presentation we hope that it
helps you in giving some kind of
information on the topic thestructure of the atom
• For your cooperation with us duringour presentation we hope that it
helps you in giving some kind of
information on the topic thestructure of the atom