1
THE STRUCTURE OF THE ATOM
THE STRUCTURE OF THE ATOM
ATOMIC MODELSATOMIC MODELS
PIONEERS OF THE ATOMPIONEERS OF THE ATOM
•DEMOCRITUS
•LAVOISIER
•DALTON
•THOMPSON
•RUTHERFORD
•BOHR
•DEMOCRITUS
•LAVOISIER
•DALTON
•THOMPSON
•RUTHERFORD
•BOHR
THE EARLY ATOMTHE EARLY ATOM
•DEMOCRITUS
IS THE MAN!!!
•YOU KNOW IT!
•DEMOCRITUS
IS THE MAN!!!
•YOU KNOW IT!
IT’S ALL
GREEK
TO ME...
2
DEMOCRITUSDEMOCRITUS• HE PROPOSED THAT ALL THE MATTER IN THE UNIVERSE IS COMPOSED OF TINY PARTICLES
• THESE PARTICLES ARE INDIVISABLE
• HE CALLED THESE PARTICLES ATOMOS (MEANS INDIVISABLE)
• BUT HE HAD AN OPPONENT…
• HE PROPOSED THAT ALL THE MATTER IN THE UNIVERSE IS COMPOSED OF TINY PARTICLES
• THESE PARTICLES ARE INDIVISABLE
• HE CALLED THESE PARTICLES ATOMOS (MEANS INDIVISABLE)
• BUT HE HAD AN OPPONENT…
ARISTOTLE = SCEPTICARISTOTLE = SCEPTIC
DEMOCRITUS IS
AN
IGNORAMUS!
ARISTOTLE WAS
MUCH MORE
POPULAR AND HE
OPPOSED THE IDEA
OF ATOMS!
ARISTOTLE WAS
MUCH MORE
POPULAR AND HE
OPPOSED THE IDEA
OF ATOMS!
ARISTOTLE = SCEPTICARISTOTLE = SCEPTIC
DEMOCRITUS IS
AN
IGNORAMUS!
ARISTOTLE
BELIEVED THAT
MATTER WAS
CONTINUOUS.
ARISTOTLE
BELIEVED THAT
MATTER WAS
CONTINUOUS.
3
DEMOCRITUS’
ATOMS
DEMOCRITUS’
ATOMS
SO...CHEMISTRY DIED
FOR ABOUT 1400 YEARS
SO...CHEMISTRY DIED
FOR ABOUT 1400 YEARS
UNTIL...UNTIL...
SO...CHEMISTRY DIED
FOR ABOUT 1400 YEARS
SO...CHEMISTRY DIED
FOR ABOUT 1400 YEARS
IN THE
1700’S
IN THE
1700’S
4
FOUNDATIONS OF ATOMIC THEORYFOUNDATIONS OF ATOMIC THEORY
• THE PREDOMINATE BELIEF BY THE MID 1700’S WAS THE MODERN DEFINITION OF AN ELEMENT AS A SUBSTANCE THAT CANNOT BE BROKEN DOWN BY ORDINARY CHEMICAL MEANS
• THE PREDOMINATE BELIEF BY THE MID 1700’S WAS THE MODERN DEFINITION OF AN ELEMENT AS A SUBSTANCE THAT CANNOT BE BROKEN DOWN BY ORDINARY CHEMICAL MEANS
FOUNDATIONS OF ATOMIC THEORYFOUNDATIONS OF ATOMIC THEORY
• IT WAS ALSO BELIEVED THAT ELEMENTS COMBINE TO FORM COMPOUNDS THAT HAVE DIFFERENT PHYS AND CHEM PROPERTIES THAN THOSE OF THE ELEMENTS THAT FORM THEM.
• IT WAS ALSO BELIEVED THAT ELEMENTS COMBINE TO FORM COMPOUNDS THAT HAVE DIFFERENT PHYS AND CHEM PROPERTIES THAN THOSE OF THE ELEMENTS THAT FORM THEM.
FOUNDATIONS OF ATOMIC THEORYFOUNDATIONS OF ATOMIC THEORY
• HOWEVER, THERE WAS CONTROVERSY AS TO WHETHER ELEMENTS ALWAYS COMBINE IN THE SAME RATIO WHEN FORMING A PARTICULAR COMPOUND.
• HOWEVER, THERE WAS CONTROVERSY AS TO WHETHER ELEMENTS ALWAYS COMBINE IN THE SAME RATIO WHEN FORMING A PARTICULAR COMPOUND.
5
FOUNDATIONS OF ATOMIC THEORYFOUNDATIONS OF ATOMIC THEORY
• IN THE 1790’S, THE STUDY OF MATTER WAS REVOLUTIONIZED BY A NEW EMPHASIS ON THE QUANTITATIVE ANALYSIS
–SCIENTISTS’ INVESTIGATIONS WERE MADE MORE ACCURATE BY NEW IMPROVED BALANCES
• IN THE 1790’S, THE STUDY OF MATTER WAS REVOLUTIONIZED BY A NEW EMPHASIS ON THE QUANTITATIVE ANALYSIS
–SCIENTISTS’ INVESTIGATIONS WERE MADE MORE ACCURATE BY NEW IMPROVED BALANCES
MATTER CAN BE
NEITHER CREATED
NOR DESTROYED.
ANTOINNE LAVOISIER TOOK ADVANTAGE… ANTOINNE LAVOISIER TOOK ADVANTAGE…
HE BEGAN TO GATHER
EVIDENCE ABOUT HOW
MATTER BEHAVED
BEFORE AND AFTER A
REACTION.
HE BEGAN TO GATHER
EVIDENCE ABOUT HOW
MATTER BEHAVED
BEFORE AND AFTER A
REACTION.
MATTER CAN BE
NEITHER CREATED
NOR DESTROYED.
ANTOINNE LAVOISIER TOOK ADVANTAGE… ANTOINNE LAVOISIER TOOK ADVANTAGE…
HE DISCOVERED THAT THE TOTAL MASS OF THE INGREDIENTS OF A
CHEMICAL REACTION WAS THE SAME AS THE TOTAL MASS OF THE RESULTS
HE DISCOVERED THAT THE TOTAL MASS OF THE INGREDIENTS OF A
CHEMICAL REACTION WAS THE SAME AS THE TOTAL MASS OF THE RESULTS
6
THE LAW OF
DEFINITE
PROPORTION
THE LAW OF
MULTIPLE
PROPORTIONS
I’M BETTER
LOOKING THAN
PROUST!
7
LAW OF
DEFINITE
PROPOR-
TIONS
A CHEM COMPD IS ALWAYS COMPOSED OF THE SAME ELEM. IN THE SAME PROPOR. BY MASS
LAW OF
MULTIPLE
PROPOR-
TIONS
IF 2 DIFFERENT COMPDS ARE COMPOSED OF THE SAME 2
ELEMTS, THEN THE RATIO OF OF THE ELEMNTS IS ALWAYS A RATIO OF SMALL WHOLE #’S
++ ==
C O CO
CARBON MONOXIDECARBON
MONOXIDE
++ ==
C O CO
CARBON MONOXIDECARBON
MONOXIDE
++ ==
C O CO2
CARBON DIOXIDECARBON DIOXIDE
++
O
DALTON’S THOUGHTSDALTON’S THOUGHTS• IN 1808, JOHN DALTON PROPOSED AN EXPLANATION FOR THE LAW OF CONS OF MASS, THE LAW OF DEFINITE PROPORTIONS, & FORMULATED THE LAW OF MULTIPLE PROPORTIONS.
• IN 1808, JOHN DALTON PROPOSED AN EXPLANATION FOR THE LAW OF CONS OF MASS, THE LAW OF DEFINITE PROPORTIONS, & FORMULATED THE LAW OF MULTIPLE PROPORTIONS.
DALTON’S THOUGHTSDALTON’S THOUGHTS• HE REASONED THAT ELEMENTS WERE COMPOSED OF ATOMS & THAT ONLY WHOLE #’S OF ATOMSCAN COMBINE TO FORM COMPNDS
• HE REASONED THAT ELEMENTS WERE COMPOSED OF ATOMS & THAT ONLY WHOLE #’S OF ATOMSCAN COMBINE TO FORM COMPNDS
8
DALTON’S THOUGHTSDALTON’S THOUGHTS• HIS IDEAS ARE NOW CALLED THE ATOMIC THEORY OF MATTER AND CAN BE SUMMARIZED AS:
• HIS IDEAS ARE NOW CALLED THE ATOMIC THEORY OF MATTER AND CAN BE SUMMARIZED AS:
1.ALL MATTER IS
COMPOSED OF
EXTREMELY SMALL
PARTICLES CALLED ATOMS
2.ATOMS OF A GIVEN
ELEMENT ARE IDENTICAL
IN SIZE, MASS, AND OTHER
PROPERTIES; ATOMS OF
DIFFERENT ELEMENTS
DIFFER IN SIZE, MASS, &
OTHER PROPERTIES
ELEMENT
2
ELEMENT
2
ELEMENT
3
ELEMENT
3
ELEMENT
4
ELEMENT
4
3.ATOMS CANNOT BE SUBDIVIDED, CREATED, OR DESTROYED
4.ATOMS OF DIFFERENT ELEMENTS COMBINE IN SIMPLE WHOLE # RATIOSTO FORM CHEM COMPDS
5.IN CHEMICAL RXNS, ATOMS ARE COMBINED, SEPARATED, OR REARRANGED
++ ++
9
DALTON AND HIS
CONTEMPORARIES
DALTON AND HIS
CONTEMPORARIES
THE EARLIEST THEORISTS
THOUGHT THE ATOM WAS
HARD AND ROUND,
MUCH LIKE TINY MARBLES
OR BALL BEARINGS.
THE EARLIEST THEORISTS
THOUGHT THE ATOM WAS
HARD AND ROUND,
MUCH LIKE TINY MARBLES
OR BALL BEARINGS.
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• ALTHOUGH DALTON THOUGHT ATOMS WERE INDIVISIBLE, INVESTIGATORS IN THE LATE 1800’S PROVED OTHERWISE
• ALTHOUGH DALTON THOUGHT ATOMS WERE INDIVISIBLE, INVESTIGATORS IN THE LATE 1800’S PROVED OTHERWISE
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• IT SOON BECAME CLEAR THAT ATOMS ARE ACTUALLY COMPOSED OF SEVERAL BASIC TYPES OF SMALLER PARTICLES
• IT SOON BECAME CLEAR THAT ATOMS ARE ACTUALLY COMPOSED OF SEVERAL BASIC TYPES OF SMALLER PARTICLES
10
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• AND IT’S THE NUMBERS AND ARRANGEMENTS OF THESE SUB-ATOMIC PARTICLES THAT DETERMINES THE IDENTITY OF THE ATOM.
• AND IT’S THE NUMBERS AND ARRANGEMENTS OF THESE SUB-ATOMIC PARTICLES THAT DETERMINES THE IDENTITY OF THE ATOM.
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• THE FIRST DISCOVERY OF A SUBATOMIC PARTICLE RESULTED FROM THE INVESTIGATIONS INTO THE RELATIONSHIP BETWEEN ELECTRICITY AND MATTER.
• THE FIRST DISCOVERY OF A SUBATOMIC PARTICLE RESULTED FROM THE INVESTIGATIONS INTO THE RELATIONSHIP BETWEEN ELECTRICITY AND MATTER.
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• IN THE LATE 1800’S, MANY EXPERIMENTS WERE PERFORMED IN WHICH ELECTRIC CURRENT WAS PASSED THROUGH VARIOUS GASES AT LOW PRESS
–CARRIED OUT IN TUBES CALLED CATHODE-RAY TUBES
• IN THE LATE 1800’S, MANY EXPERIMENTS WERE PERFORMED IN WHICH ELECTRIC CURRENT WAS PASSED THROUGH VARIOUS GASES AT LOW PRESS
–CARRIED OUT IN TUBES CALLED CATHODE-RAY TUBES
11
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• INVESTIGATORS NOTICED THAT WHEN CURRENT WAS PASSED THROUGH A CATHODE RAY TUBE, THE SURFACE OF THE TUBE DIRECTLY OPPOSITE THE CATHODE GLOWED.
• INVESTIGATORS NOTICED THAT WHEN CURRENT WAS PASSED THROUGH A CATHODE RAY TUBE, THE SURFACE OF THE TUBE DIRECTLY OPPOSITE THE CATHODE GLOWED.
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• THEY HYPOTHESIZED THAT THE GLOW WAS CAUSED BY A STREAM OF PARTICLES
–THEY CALLED THE STREAM A CATHODE RAY
• THEY HYPOTHESIZED THAT THE GLOW WAS CAUSED BY A STREAM OF PARTICLES
–THEY CALLED THE STREAM A CATHODE RAY
STRUCTURE OF THE ATOMSTRUCTURE OF THE ATOM• THE CATHODE RAY TRAVELED FROM THE CATHODE TO THE ANODE WHEN CURRENT WAS PASSED THROUGH THE TUBE.
• THE CATHODE RAY TUBE OPENED THE DOOR FOR J.J. THOMPSON
• THE CATHODE RAY TRAVELED FROM THE CATHODE TO THE ANODE WHEN CURRENT WAS PASSED THROUGH THE TUBE.
• THE CATHODE RAY TUBE OPENED THE DOOR FOR J.J. THOMPSON
12
J. J. THOMPSONJ. J. THOMPSON
I PLAY WITH
ELECTRONS
• THOMPSON’S INVESTIGATIONS SUPPLIED EVIDENCE THAT THE CATHODE RAY COULD BE DEFLECTED BY APPLYING A POSITIVELY CHARGED ELECTRIC FIELD
–THIS HELPED THOMPSON DISC-OVER THAT THE CATHODE RAY WAS NEGATIVELY CHARGED.
• THOMPSON’S INVESTIGATIONS SUPPLIED EVIDENCE THAT THE CATHODE RAY COULD BE DEFLECTED BY APPLYING A POSITIVELY CHARGED ELECTRIC FIELD
–THIS HELPED THOMPSON DISC-OVER THAT THE CATHODE RAY WAS NEGATIVELY CHARGED.
J. J. THOMPSONJ. J. THOMPSON
13
• THOMPSON WAS ABLE TO MEASURE THE RATIO OF THE CHARGE OF CATHODE RAY PARTICLES TO THEIR MASS
–HE FOUND THAT THE RATIO WAS THE SAME REGARDLESS OF THE METAL USED AS THE CATHODE
• THOMPSON WAS ABLE TO MEASURE THE RATIO OF THE CHARGE OF CATHODE RAY PARTICLES TO THEIR MASS
–HE FOUND THAT THE RATIO WAS THE SAME REGARDLESS OF THE METAL USED AS THE CATHODE
• THOMPSON CONCLUDED THAT ALL CATHODE RAYS ARE COMPOSED OFIDENTICAL NEGATIVELY CHARGED PARTICLES
–WHICH WERE LATER CALLED ELECTRONS
• THOMPSON CONCLUDED THAT ALL CATHODE RAYS ARE COMPOSED OFIDENTICAL NEGATIVELY CHARGED PARTICLES
–WHICH WERE LATER CALLED ELECTRONS
• HE PROPOSED THAT THE ATOM LOOKS SOMETHING LIKE ACHOCOLATE CHIP COOKIE
• HE PROPOSED THAT THE ATOM LOOKS SOMETHING LIKE ACHOCOLATE CHIP COOKIE
THOMPSON’S ATOMIC MODELTHOMPSON’S ATOMIC MODEL
THE COOKIE PART IS POS. MATTER TO
CANCEL OUT THE NEG. ELECTRONS
THE COOKIE PART IS POS. MATTER TO
CANCEL OUT THE NEG. ELECTRONS
THE CHIPS WOULD BE
HIS ELECTRONS
THE CHIPS WOULD BE
HIS ELECTRONS
14
• THOMPSON’S EXPERIMENTS REVEALED THAT THE ELECTRON HAS A VERY LARGE CHARGE IN RELATION TO ITS MASS
• THOMPSON’S EXPERIMENTS REVEALED THAT THE ELECTRON HAS A VERY LARGE CHARGE IN RELATION TO ITS MASS
• IN 1909, ROBERT MILLIKAN, PERFORMED AN INGENIOUS EXPERIMENT TO CALCULATE THEMASS OF AN ELECTRON
–HE DISCOVERED THAT THE MASS OF THE ELECTRON IS ABOUT 1/2000TH
THE MASS OF THE SIMPLEST ATOM (HYDRO.)
• IN 1909, ROBERT MILLIKAN, PERFORMED AN INGENIOUS EXPERIMENT TO CALCULATE THEMASS OF AN ELECTRON
–HE DISCOVERED THAT THE MASS OF THE ELECTRON IS ABOUT 1/2000TH
THE MASS OF THE SIMPLEST ATOM (HYDRO.)
HELLO, MILLIKANHELLO, MILLIKAN
DAT’S RIGHT!
I SAVED THE
DAY!
15
• HIS OIL DROP EXPERIMENT SHOWED THAT EVEN THOUGH THE ATOMS OF DIFFERENT ELEMENTS ARE VERY DIFFERENT, THEIR ELECTRONS ARE IDENTICAL.
–AN ELECTRON IS AN ELECTRON
–THE DIFFERENCE BETWEEN TWO DIFFERENT ATOMS IS THEIR NUMBER OF ELECTRONS NOT THEIR TYPE OF ELECTRON.
• HIS OIL DROP EXPERIMENT SHOWED THAT EVEN THOUGH THE ATOMS OF DIFFERENT ELEMENTS ARE VERY DIFFERENT, THEIR ELECTRONS ARE IDENTICAL.
–AN ELECTRON IS AN ELECTRON
–THE DIFFERENCE BETWEEN TWO DIFFERENT ATOMS IS THEIR NUMBER OF ELECTRONS NOT THEIR TYPE OF ELECTRON.
• HE ALSO CALCULATED THAT THE ELECTRON’S MASS IS 9.109x10-31kg
• HE ALSO CALCULATED THAT THE ELECTRON’S MASS IS 9.109x10-31kg
SO FAR WE’VE LEARNED…SO FAR WE’VE LEARNED…• THOMPSON’S & MILLIKAN’S IDEAS:
–ATOMS ARE IN FACT DIVISABLE
• THOMPSON’S & MILLIKAN’S IDEAS:
–ATOMS ARE IN FACT DIVISABLE
16
SO FAR WE’VE LEARNED…SO FAR WE’VE LEARNED…• THOMPSON’S & MILLIKAN’S IDEAS:
–ELECTRONS ARE PRESENT IN ATOMS OF ALL ELEMENTS
• THOMPSON’S & MILLIKAN’S IDEAS:
–ELECTRONS ARE PRESENT IN ATOMS OF ALL ELEMENTS
SO FAR WE’VE LEARNED…SO FAR WE’VE LEARNED…• THOMPSON’S & MILLIKAN’S IDEAS:
–ONE OF THE ATOM’S FUNDEMENTAL PARTICLES IS NEGATIVELY CHARGED
• THOMPSON’S & MILLIKAN’S IDEAS:
–ONE OF THE ATOM’S FUNDEMENTAL PARTICLES IS NEGATIVELY CHARGED
SO FAR WE’VE LEARNED…SO FAR WE’VE LEARNED…• THOMPSON’S & MILLIKAN’S IDEAS:
–ATOMS ARE ELECTRICALLY NEUTRAL, SO THERE MUST BE A (+) CHARGE TO BALANCE OUT THE (–)
• THOMPSON’S & MILLIKAN’S IDEAS:
–ATOMS ARE ELECTRICALLY NEUTRAL, SO THERE MUST BE A (+) CHARGE TO BALANCE OUT THE (–)
17
SO FAR WE’VE LEARNED…SO FAR WE’VE LEARNED…• THOMPSON’S & MILLIKAN’S IDEAS:
–BECAUSE ELECTRONS ARE BASICALLY MASSLESS THERE MUST BE SOMETHING ELSE THAT ACCOUNTS FOR THE ATOMS MASS.
• THOMPSON’S & MILLIKAN’S IDEAS:
–BECAUSE ELECTRONS ARE BASICALLY MASSLESS THERE MUST BE SOMETHING ELSE THAT ACCOUNTS FOR THE ATOMS MASS.
OTHER SIGNIFICANT DISCOVERIES…
OTHER SIGNIFICANT DISCOVERIES…
• IN 1886, WHEN E. GOLDSTEIN OBSERVED A CATHODE-RAY TUBE AND FOUND RAYS TRAVELLING IN THE OPPOSITE DIRECTION OF THAT OF THE CATHODE RAYS
–HE CALLED THE RAYS CANAL RAYSAND CONCLUDED THAT THEY WERE COMPOSED OF POS. PARTICLES
• IN 1886, WHEN E. GOLDSTEIN OBSERVED A CATHODE-RAY TUBE AND FOUND RAYS TRAVELLING IN THE OPPOSITE DIRECTION OF THAT OF THE CATHODE RAYS
–HE CALLED THE RAYS CANAL RAYSAND CONCLUDED THAT THEY WERE COMPOSED OF POS. PARTICLES
OTHER SIGNIFICANT DISCOVERIES…
OTHER SIGNIFICANT DISCOVERIES…
• IT WAS SOON DISCOVERED THAT THE POSITIVE PARTICLES MASS IS ABOUT 2000 TIMESTHAT OF THE ELECTRON
• IT WAS SOON DISCOVERED THAT THE POSITIVE PARTICLES MASS IS ABOUT 2000 TIMESTHAT OF THE ELECTRON
18
• IN 1932, THE ENGLISH PHYSICIST JAMES CHADWICK CONFIRMED THE EXISTANCE OF YET ANOTHER SUBATOMIC PARTICLE.
–THE NEUTRON, WHICH IS A PARTICLE WITH NO CHARGE
–HAS A MASS NEARLY EQUALTO THAT OF THE PROTON
• IN 1932, THE ENGLISH PHYSICIST JAMES CHADWICK CONFIRMED THE EXISTANCE OF YET ANOTHER SUBATOMIC PARTICLE.
–THE NEUTRON, WHICH IS A PARTICLE WITH NO CHARGE
–HAS A MASS NEARLY EQUALTO THAT OF THE PROTON
OTHER SIGNIFICANT DISCOVERIES…
OTHER SIGNIFICANT DISCOVERIES…
• THEREFORE THE SUBATOMIC PARTICLES ARE THE ELECTRON, PROTON, AND NEUTRON.
• THEREFORE THE SUBATOMIC PARTICLES ARE THE ELECTRON, PROTON, AND NEUTRON.
OTHER SIGNIFICANT DISCOVERIES…
OTHER SIGNIFICANT DISCOVERIES…
electron e- -1 0 9.11x10-28
proton p+ +1 1 1.67x10-24
neutron n0 0 1 1.67x10-24
19
• WHEN SUBATOMIC PARTICLES WERE DISCOVERED, SCIENTISTS WONDERED HOW THESE PARTICLES WERE PUT TOGETHER IN AN ATOM.
• WHEN SUBATOMIC PARTICLES WERE DISCOVERED, SCIENTISTS WONDERED HOW THESE PARTICLES WERE PUT TOGETHER IN AN ATOM.
THE ATOMIC NUCLEUSTHE ATOMIC NUCLEUS
• THIS WAS A DIFFICULT QUESTION TO ANSWER, GIVEN HOW TINY ATOMS ARE.
• THIS WAS A DIFFICULT QUESTION TO ANSWER, GIVEN HOW TINY ATOMS ARE.
THE ATOMIC NUCLEUSTHE ATOMIC NUCLEUS
• MOST SCIENTISTS THOUGHT IT LIKELY THAT THE ELECTRONS WERE EVENLY DISTRIBUTED THROUGHOUT AN ATOM FILLED UNIFORMLY WITH POSITIVELY CHARGED MATERIAL.
• MOST SCIENTISTS THOUGHT IT LIKELY THAT THE ELECTRONS WERE EVENLY DISTRIBUTED THROUGHOUT AN ATOM FILLED UNIFORMLY WITH POSITIVELY CHARGED MATERIAL.
THE ATOMIC NUCLEUSTHE ATOMIC NUCLEUS
20
ERNEST RUTHERFORDERNEST RUTHERFORD
HOW IS THE
ATOM BUILT?
IN 1911, RUTHERFORD
PERFORMED ONE OF
THE MOST BRILLIANT
INVESTIGATIONS
EVER CONCIEVED.
IN 1911, RUTHERFORD
PERFORMED ONE OF
THE MOST BRILLIANT
INVESTIGATIONS
EVER CONCIEVED.
RUTHERFORD’S FAMOUS EXPERIMENT
RUTHERFORD’S FAMOUS EXPERIMENT
• RUTHERFORD SET OUT TO TEST THE THOMPSON MODEL OF THE ATOM
• RUTHERFORD SET OUT TO TEST THE THOMPSON MODEL OF THE ATOM
RUTHERFORD’S FAMOUS EXPERIMENT
RUTHERFORD’S FAMOUS EXPERIMENT
• THE TEST USED RELATIVELY MASSIVE RADIOACTIVE ALPHA PARTICLES–ALPHA PARTICLES (αααα) ARE HELIUM ATOMS THAT HAVE LOST THEIR 2 ELECTRONS AND HAVE A DOUBLE POSITIVE CHARGE BECAUSE OF THE 2 REMAINING PROTONS
• THE TEST USED RELATIVELY MASSIVE RADIOACTIVE ALPHA PARTICLES–ALPHA PARTICLES (αααα) ARE HELIUM ATOMS THAT HAVE LOST THEIR 2 ELECTRONS AND HAVE A DOUBLE POSITIVE CHARGE BECAUSE OF THE 2 REMAINING PROTONS
21
• IN THE EXPERIMENT, RUTHERFORD DIRECTED A NARROW BEAM OF ALPHA PARTICLES AT A VERY THIN SHEET OF GOLD FOIL.–ACCORDING TO THE PREVAILING THEORY, THE ALPHA PARTICLES SHOULD HAVE PASSED EASILY THROUGH THE GOLD, WITH ONLY A SLIGHT DEFLECTION DUE TO THE POSITIVE CHARGE THOUGHT TO BE SPREAD OUT IN THE GOLD ATOMS.
• IN THE EXPERIMENT, RUTHERFORD DIRECTED A NARROW BEAM OF ALPHA PARTICLES AT A VERY THIN SHEET OF GOLD FOIL.–ACCORDING TO THE PREVAILING THEORY, THE ALPHA PARTICLES SHOULD HAVE PASSED EASILY THROUGH THE GOLD, WITH ONLY A SLIGHT DEFLECTION DUE TO THE POSITIVE CHARGE THOUGHT TO BE SPREAD OUT IN THE GOLD ATOMS.
22
WHAT HAPPENED?WHAT HAPPENED?• THE MAJORITY OF THE αααα PARTICLES PASSED STRAIGHT THROUGH THE GOLD ATOMS, WITHOUT ANY DEFLECTION
• THE MAJORITY OF THE αααα PARTICLES PASSED STRAIGHT THROUGH THE GOLD ATOMS, WITHOUT ANY DEFLECTION
WHAT HAPPENED?WHAT HAPPENED?• EVEN MORE SURPRISINGLY, A SMALL FRACTION OF THE ααααPARTICLES BOUNCED OFF THE GOLD FOIL ATOMS AT VERY LARGE ANGLES
• EVEN MORE SURPRISINGLY, A SMALL FRACTION OF THE ααααPARTICLES BOUNCED OFF THE GOLD FOIL ATOMS AT VERY LARGE ANGLES
23
WHAT HAPPENED?WHAT HAPPENED?• SOME EVEN BOUNCED BACK AT THE SOURCE
• SOME EVEN BOUNCED BACK AT THE SOURCE
• BASED ON THE RESULTS, RUTHERFORD SUGGESTED A NEW THEORY OF THE ATOM.
• BASED ON THE RESULTS, RUTHERFORD SUGGESTED A NEW THEORY OF THE ATOM.
• HE PROPOSED THAT THE ATOM ISMOSTLY EMPTY SPACE–THIS EXPLAINED THE LACK OF DEFLECTION OF SOME OF THE PARTICLES
• HE PROPOSED THAT THE ATOM ISMOSTLY EMPTY SPACE–THIS EXPLAINED THE LACK OF DEFLECTION OF SOME OF THE PARTICLES
24
• HE CONCLUDED THAT ALL THE POSITIVE CHARGE AND ALMOST ALL THE MASS IS CONCENTRATED IN A SMALL CORE–HE CALLED THIS REGION THE NUCLEUS
• HE CONCLUDED THAT ALL THE POSITIVE CHARGE AND ALMOST ALL THE MASS IS CONCENTRATED IN A SMALL CORE–HE CALLED THIS REGION THE NUCLEUS
NIELS BOHR
25
NIELS BOHR
I play with light!
Bohr
• Refined Rutherford’s idea
–Added ORBITS like planets
orbiting the sun
–Orbits = Energy Levels or Shells
or Shields
• Refined Rutherford’s idea
–Added ORBITS like planets
orbiting the sun
–Orbits = Energy Levels or Shells
or Shields
Bohr’s Atom
electrons in orbits
nucleus
26
ENERGY LEVELS
• Energy level Maximum # e-
–1st 2
–2nd 8
–3rd 18
–4th 32
• Energy level Maximum # e-
–1st 2
–2nd 8
–3rd 18
–4th 32
A LITTLE REVIEW!A LITTLE REVIEW!• THERE ARE THREE FUNDAMENTAL PARTICLES THAT TOGETHER MAKE UP THE ATOM.–COMPOSED OF ELECTRONS, PROTONS, AND NEUTRONS
• THERE ARE THREE FUNDAMENTAL PARTICLES THAT TOGETHER MAKE UP THE ATOM.–COMPOSED OF ELECTRONS, PROTONS, AND NEUTRONS
A LITTLE REVIEW!A LITTLE REVIEW!• THE PROTONS AND THE NEUTRONS MAKE UP THE CENTER OF THE ATOM–CENTER OF THE ATOM IS CALLED THE NUCLEUS
• THE PROTONS AND THE NEUTRONS MAKE UP THE CENTER OF THE ATOM–CENTER OF THE ATOM IS CALLED THE NUCLEUS
27
A LITTLE REVIEW!A LITTLE REVIEW!• THE PROTONS & NEUTRONS OCC-UPY THE MASS OF THE ATOM
• THE PROTONS & NEUTRONS OCC-UPY THE MASS OF THE ATOM
• THE ELECTRONS SURROUND THE NUCLEUS AND OCCUPY MOST OF THE ATOM’S VOLUME
• THE ELECTRONS SURROUND THE NUCLEUS AND OCCUPY MOST OF THE ATOM’S VOLUME
• HOW, THEN, ARE ATOMS OF HYDROGEN DIFFERENT FROM THOSE OF OXYGEN?
–A SUBATOMIC PARTICLES FROM ONE TYPE OF ATOM LOOKS LIKE PARTICLES FROM OTHER ATOMS
• HOW, THEN, ARE ATOMS OF HYDROGEN DIFFERENT FROM THOSE OF OXYGEN?
–A SUBATOMIC PARTICLES FROM ONE TYPE OF ATOM LOOKS LIKE PARTICLES FROM OTHER ATOMS
28
• IT’S THE NUMBERS OF PROTONS IN AN ATOM THAT MAKES ATOMS DIFFERENT.
–AN OXYGEN ATOM HAS 8 PROTONSIN ITS NUCLEUS
–A HYDROGEN ATOM HAS 1 PROTONIN ITS NUCLEUS
• IT’S THE NUMBERS OF PROTONS IN AN ATOM THAT MAKES ATOMS DIFFERENT.
–AN OXYGEN ATOM HAS 8 PROTONSIN ITS NUCLEUS
–A HYDROGEN ATOM HAS 1 PROTONIN ITS NUCLEUS
• THE ATOMIC NUMBER OF AN ELEMENT IS THE NUMBER OF PROTONS IN THE NUCLEUS OF AN ATOM OF THAT ELEMENT
–SINCE OXYGEN’S NUCLEUS HAS 8 PROTONS ITS ATOMIC # IS 8
• THE ATOMIC NUMBER OF AN ELEMENT IS THE NUMBER OF PROTONS IN THE NUCLEUS OF AN ATOM OF THAT ELEMENT
–SINCE OXYGEN’S NUCLEUS HAS 8 PROTONS ITS ATOMIC # IS 8
• THE PROTONS IDENTIFY THE TYPEOF ATOM, THE ONLY ATOM WITH 8 PROTONS IS OXYGEN
• THE PROTONS IDENTIFY THE TYPEOF ATOM, THE ONLY ATOM WITH 8 PROTONS IS OXYGEN
29
ATOMS OF THE 1STTEN ATOMS
Hydrogen H 1 1 0 1 1
Helium He 2 2 2 4 2
Lithium Li 3 3 4 7 3
Beryllium Be 4 4 5 9 4
Boron B 5 5 6 11 5
Carbon C 6 6 6 12 6
Nitrogen N 7 7 7 14 7
Oxygen O 8 8 8 16 8
Fluorine F 9 9 10 19 9
Neon Ne 10 10 10 20 10
• FOR EACH ELEMENT LISTED, THE NUMBER OF PROTONS EQUALS THE NUMBER OF ELECTRONS
–REMEMBER ATOMS ARE ELECTRICALLY NEUTRAL
• FOR EACH ELEMENT LISTED, THE NUMBER OF PROTONS EQUALS THE NUMBER OF ELECTRONS
–REMEMBER ATOMS ARE ELECTRICALLY NEUTRAL
30
ATOMS OF THE 1STTEN ATOMS
Hydrogen H 1 1 0 1 1
Helium He 2 2 2 4 2
Lithium Li 3 3 4 7 3
Beryllium Be 4 4 5 9 4
Boron B 5 5 6 11 5
Carbon C 6 6 6 12 6
Nitrogen N 7 7 7 14 7
Oxygen O 8 8 8 16 8
Fluorine F 9 9 10 19 9
Neon Ne 10 10 10 20 10
• IN AN ATOM, THE NUMBER OF ELECTRONS MUST EQUAL THE NUMBER OF PROTONS
• A HYDROGEN ATOM HAS 1 ELECTRN• AN OXYGEN ATOM HAS 8 ELECTRNS
• IN AN ATOM, THE NUMBER OF ELECTRONS MUST EQUAL THE NUMBER OF PROTONS
• A HYDROGEN ATOM HAS 1 ELECTRN• AN OXYGEN ATOM HAS 8 ELECTRNS
• THE MASS OF AN ATOM IS CONCENTRATED IN ITS NUCLEUS AND DEPENDS ON THE NUMER OF PROTONS AND NEUTRONS
• MASS # = #P+ + #NO
• THE MASS OF AN ATOM IS CONCENTRATED IN ITS NUCLEUS AND DEPENDS ON THE NUMER OF PROTONS AND NEUTRONS
• MASS # = #P+ + #NO
31
ATOMS OF THE 1STTEN ATOMS
Hydrogen H 1 1 0 1 1
Helium He 2 2 2 4 2
Lithium Li 3 3 4 7 3
Beryllium Be 4 4 5 9 4
Boron B 5 5 6 11 5
Carbon C 6 6 6 12 6
Nitrogen N 7 7 7 14 7
Oxygen O 8 8 8 16 8
Fluorine F 9 9 10 19 9
Neon Ne 10 10 10 20 10
• THE COMPOSITION OF ANY ATOM CAN BE REPRESENTED IN SHORTHAND NOTATION:
• THE COMPOSITION OF ANY ATOM CAN BE REPRESENTED IN SHORTHAND NOTATION:
CHEMICAL COMPOSITION SHORTHAND
CHEMICAL COMPOSITION SHORTHAND
ClCl3535
1717
MASS
NUMBER
MASS
NUMBER
ATOMIC
NUMBER
ATOMIC
NUMBER
NUMBER OF
PROTONS
NUMBER OF
PROTONS
# OF PROTONS+
# OF NEUTRONS
# OF PROTONS+
# OF NEUTRONS
32
• EVERY CHLORINE ATOM HAS 17 PROTONS, WITHOUT EXCEPTION, –HOWEVER, NOT EVERY CHLORINE ATOM HAS 18 NEUTRONS.
–ATOMS WITH THE SAME NUMBER OF PROTONS BUT CONTAIN DIFFERENT NUMBERS OF NEUTRONS ARE CALLED ISOTOPES.
• EVERY CHLORINE ATOM HAS 17 PROTONS, WITHOUT EXCEPTION, –HOWEVER, NOT EVERY CHLORINE ATOM HAS 18 NEUTRONS.
–ATOMS WITH THE SAME NUMBER OF PROTONS BUT CONTAIN DIFFERENT NUMBERS OF NEUTRONS ARE CALLED ISOTOPES.
ISOTOPESISOTOPES
• BECAUSE ISOTOPES OF AN ELEMENT HAVE DIFFERENT NUMBERS OF NEUTRONS THEY HAVEDIFFERENT MASS NUMBERS.
• BECAUSE ISOTOPES OF AN ELEMENT HAVE DIFFERENT NUMBERS OF NEUTRONS THEY HAVEDIFFERENT MASS NUMBERS.
ISOTOPESISOTOPES
33
• ISOTOPES ARE CHEMICALLY ALIKE BECAUSE THEY HAVE IDENTICAL NUMBERS OF PROTONS AND ELECTRONS– IT’S THE ELECTRONS AND PROTONS THAT ARE RESPONSIBLE FOR CHEMICAL BEHAVIOR
• ISOTOPES ARE CHEMICALLY ALIKE BECAUSE THEY HAVE IDENTICAL NUMBERS OF PROTONS AND ELECTRONS– IT’S THE ELECTRONS AND PROTONS THAT ARE RESPONSIBLE FOR CHEMICAL BEHAVIOR
proton
neutronneutron
electronelectron
BERYLLIUM
ISOTOPES
BERYLLIUM
ISOTOPES
EXAMPLE OF AN
ISOTOPE
EXAMPLE OF AN
ISOTOPE
ClCl3535
1717 ClCl3737
1717
20 20 NEUTRONSNEUTRONS
ATOMIC MASS
1818 NEUTRONSNEUTRONS
ATOMIC NUMBER
34
IONSIONS• AN ELEMENT’S ATOMS ARE NOT ALWAYS NEUTRAL IN CHARGE.–WHEN AN ATOM LOSES OR GAINS ONE OR MORE OF ITS ELECTRONS IT BECOMES ION.
• AN ELEMENT’S ATOMS ARE NOT ALWAYS NEUTRAL IN CHARGE.–WHEN AN ATOM LOSES OR GAINS ONE OR MORE OF ITS ELECTRONS IT BECOMES ION.
IONSIONS• AN ION THAT HAS MORE ELECTRONS THAN PROTONS HAS ANEGATIVE ELECTRICAL CHARGE
• AN ION THAT HAS MORE ELECTRONS THAN PROTONS HAS ANEGATIVE ELECTRICAL CHARGE
IONSIONS• AN ION THAT HAS FEWER ELECTRONS THAN PROTONS HAS A POSITIVE ELECTRICAL CHARGE
• AN ION THAT HAS FEWER ELECTRONS THAN PROTONS HAS A POSITIVE ELECTRICAL CHARGE
35
IONSIONS
NOTE: IT’S THE PROTONS THAT DEFINE THE TYPE OF ATOM IT IS, BUT THE ELECTRONS DEFINE THE ATOM’S CHARGE.
NOTE: IT’S THE PROTONS THAT DEFINE THE TYPE OF ATOM IT IS, BUT THE ELECTRONS DEFINE THE ATOM’S CHARGE.
SOME ATOMS
GAIN ELECTRONS
SOME ATOMS
GAIN ELECTRONS
O
--
----
--
--
--
--
--
O-2
--
----
--
--
--
--
--
----
ATOM’S IONIC CHARGE =
# PROTONS - # ELECTRONS
ATOM’S IONIC CHARGE =
# PROTONS - # ELECTRONS
36
ATOMS, IONS, AND ISOTOPES
ATOMS
NEUTRAL AND ARE DEFINED BY THE # OF PROTONS IN THEIR
NUCLEUS
3 p+ = Li ATOM, ETC.
IONS
HAVE AN ELECTRICAL CHARGE DETERMINED BY
# PROTONS - # ELECTRONS
N-2 = 7 p+ - 9 e- ; ETC.
ISOTOPES
TWO ATOMS WITH THE SAME # OF PROTONS, BUT DIFFERENT #’S OF
NEUTRONS OR MASSES
CALCIUM-40 & CALCIUM-44