CHAPTER 3LABORATORY CHEMISTRY1 CHAPTER 3 THE STRUCTURE OF MATTER

CHAPTER 3LABORATORY CHEMISTRY2 ATOMIC STRUCTURE n 1. EARLY MODELS OF THE ATOM n 2. DISCOVERING ATOMIC STRUCTURE n 3. MODERN ATOMIC THEORY n 4. CHANGES IN THE NUCLEUS

CHAPTER 3LABORATORY CHEMISTRY3 EARLY MODELS OF THE ATOM n DEMOCRITUS: (450 BC) –“ATOMOS” n THE SMALLEST PARTICLE OF AN ELEMENT THAT RETAINS THE CHEMICAL IDENTITY OF THAT ELEMENT. n ARISTOTLE: –EARTH, AIR, FIRE, AND WATER DEMOCRITUS

CHAPTER 3LABORATORY CHEMISTRY4 EARLY MODELS OF THE ATOM n LAVOISIER, ANTON: (LATE 1700’S) –LAW OF CONSERVATION OF MATTER (AND ENERGY) n PROUST, JOSEPH: (1799) –LAW OF CONSTANT COMPOSITION n DALTON, JOHN (1803) –SCHOOL TEACHER –ATOMIC THEORY OF MATTER

CHAPTER 3LABORATORY CHEMISTRY5 EARLY MODELS OF THE ATOM n DALTON’S ATOMIC THEORY –EACH ELMENT IS COMPOSED OF EXTREMELY SMALL PARTICLES CALLED ATOMS. –ALL ATOMS OF A GIVEN ELEMENT ARE IDENTICAL, BUT THEY DIFFER FROM THOSE OF ANY OTHER ELEMENT. –ATOMS ARE NEITHER CREATED NOR DESTROYED IN ANY CHEMICAL REACTION. –A GIVEN COMPOUND ALWAYS HAS THE SAME RELATIVE NUMBERS AND KINDS OF ATOMS.

CHAPTER 3LABORATORY CHEMISTRY6 EARLY MODELS OF THE ATOM n WHY IS THERE SUCH DIVERSITY IN NATURE IF THERE ARE ONLY ABOUT 100 DIFFERENT KINDS OF ATOMS ?

CHAPTER 3LABORATORY CHEMISTRY7 DISCOVERING ATOMIC STRUCTURE n FARADAY, MICHAEL (1839) –SUGGESTED THAT THE STRUCTURE OF ATOMS WAS RELATED TO ELECTRICITY. n FRANKLIN, BENJAMIN (MID-1700’S) –STATIC ELECTRICITY –BATTERIES –“POSITIVE AND NEGATIVE CHARGES”

CHAPTER 3LABORATORY CHEMISTRY8 DISCOVERING ATOMIC STRUCTURE n CATHODE RAY TUBE –INVENTED IN THE MID-1800’S -+ ELECTRON BEAM ANODE CATHODE

CHAPTER 3LABORATORY CHEMISTRY9 DISCOVERING ATOMIC STRUCTURE –THOMSON, J.J. (1896) n DISCOVERED AND NAMED ELECTRONS n DETERMINED THE CHARGE (1.76 X 10 8 COULOMBS/GRAM) n “PLUM-PUDDING” MODEL OF THE ATOM

CHAPTER 3LABORATORY CHEMISTRY10 DISCOVERING ATOMIC STRUCTURE –RUTHERFORD, ERNEST (EARLY 1900’S) n ALPHA(2+) AND BETA(1-) RADIATION (GAMMA RADIATION WAS DISCOVERED LATER) –MADE OF PARTICLES

CHAPTER 3LABORATORY CHEMISTRY11 RUTHERFORD’S GOLD FOIL EXPERIMENT GOLD FOIL

CHAPTER 3LABORATORY CHEMISTRY12 DISCOVERING ATOMIC STRUCTURE n THE NUCLEAR ATOM –ALPHA SCATTERING EXPERIMENT (GOLD FOIL EXPERIMENT) –RUTHERFORD NAMES THE NUCLEUS AND DETERMINES ITS CHARGE –THE RUTHERFORD/BOHR MODEL OF THE ATOM Well…I’m Ernie Rutherford ! And I love a good Cigar! Hi..I’m Niels Bohr ! And I love Physics !

CHAPTER 3LABORATORY CHEMISTRY13 MODERN ATOMIC THEORY n THE STRUCTURE OF THE ATOM –NUCLEUS n PROTONS n NEUTRONS –ELECTRONS –RUTHERFORD’S VISUALIZATION (MINATURE SOLAR SYSTEM) –UNCERTAINTY (ELECTRON CLOUD)

CHAPTER 3LABORATORY CHEMISTRY14 “PLUMB- PUDDING” MODEL “SOLAR SYSTEM” MODEL

CHAPTER 3LABORATORY CHEMISTRY15 DISCOVERING ATOMIC STRUCTURE NOTE THAT EVEN THOUGH THE MASS OF AN ELECTRON IS FAR LESS THAN A PROTON….THE CHARGES ARE OF THE SAME MAGNITUDE BUT OPPOSITE 1.63 X X

CHAPTER 3LABORATORY CHEMISTRY16 DISCOVERING ATOMIC STRUCTURE n ATOMIC NUMBERS –MOSELEY, HENRY ( ) n STUDENT OF RUTHERFORD n DISCOVERED THE PROTON (UNIQUE POSITIVE CHARGE OF THE NUCLEUS) n ATOMIC NUMBER = NUMBER OF PROTONS IN THE NUCLEUS AND ALSO = THE NUMBER OF ELECTRONS AROUND THE NUCLEUS

CHAPTER 3LABORATORY CHEMISTRY17 DISCOVERING ATOMIC STRUCTURE N ATOMIC MASS ATOMIC NUMBER Atomic Symbol NITROGEN Element Name n PERIODIC TABLE 7

CHAPTER 3LABORATORY CHEMISTRY18 DISCOVERING ATOMIC STRUCTURE n WRITING THE ELEMENTS TO CALCULATE PROTONS, NEUTRONS, AND ELECTRONS –TO CALCULATE THE NUMBER OF NEUTRONS, SUBTRACT THE NUMBER OF PROTONS FROM THE ATOMIC MASS –THE NUMBER OF ELECTRONS = THE NUMBER OF PROTONS (ATOMIC NUMBER) IN A NEUTRAL ATOM

CHAPTER 3LABORATORY CHEMISTRY19 DISCOVERING ATOMIC STRUCTURE Na ATOMIC MASS “  ” IN AMU ATOMIC NUMBER “Z” NUMBER 12 NUMBER OF NEUTRONS THIS IS ALSO THE NUMBER OF ELECTRONS IN A GROUND STATE ATOM!!!!!

CHAPTER 3LABORATORY CHEMISTRY20 DISCOVERING ATOMIC STRUCTURE n IONS –WHEN AN ATOM GAINS OR LOSES AN ELECTRON IT ACQUIRES AN ELECTRICAL CHARGE –PLACE THE APPROPRIATE CHARGE SIGN AND NUMBER AT THE UPPER RIGHT OF THE ELEMENT SYMBOL N 3+ CHARGE OF AN ION = NUMBER OF PROTONS-NUMBER OF ELECTRONS O 2- Fe 2+ Cl 2- Ca 2+

CHAPTER 3LABORATORY CHEMISTRY21 PRACTICE N 7 14 N 7 +3 LOSES 3 ELECTRONS GROUND STATE ATOM NEUTRAL (NO CHARGE) (+7) + (-7) = 0 THE NUMBER OF PROTONS DO NOT CHANGE AN ION A CHARGED ATOM (+7)+( -4) = 3 + PROTONS ELECTRONS CHARGE PROTONS CHARGE ELECTRONS

CHAPTER 3LABORATORY CHEMISTRY22 DISCOVERING ATOMIC STRUCTURE n ISOTOPES –ATOMS THAT HAVE THE SAME NUMBER OF PROTONS BUT DIFFERENT NUMBERS OF NEUTRONS (OVERWEIGHT OR UNDERWEIGHT ATOMS) –NAMED BY THE ISOTOPES MASS NUMBER (PROTONS + NEUTRONS)

CHAPTER 3LABORATORY CHEMISTRY23 DISCOVERING ATOMIC STRUCTURE C 12 6 C 14 6 GROUND STATE CARBON RADIOACTIVE CARBON CARBON-12CARBON-14

CHAPTER 3LABORATORY CHEMISTRY24 DISCOVERING ATOMIC STRUCTURE n THE MASS OF AN ATOM –ATOMIC MASS UNITS (AMU) –AVERAGE MASS OF AN ELEMENT’S ATOMS IS CALLED THE ATOMIC MASS.

CHAPTER 3LABORATORY CHEMISTRY25 CHANGES IN THE NUCLEUS n NUCLEAR REACTIONS CHANGE THE COMPOSITION OF AN ATOM’S NUCLEUS. n NUCLEAR STABILITY –STABLE NUCLEUS (NOT RADIOACTIVE) n RADIOACTIVE DECAY –RADIATION (ALPHA, BETA, AND GAMMA)

CHAPTER 3LABORATORY CHEMISTRY26 CHANGES IN THE NUCLEUS n TYPES OF RADIATION

CHAPTER 3LABORATORY CHEMISTRY27 ALPHA-BETA-GAMMA SCATTERING

CHAPTER 3LABORATORY CHEMISTRY28 CHANGES IN THE NUCLEUS n Alpha decay

CHAPTER 3LABORATORY CHEMISTRY29 CHANGES IN THE NUCLEUS Hello, my name is Lise Meitner. I was born in Austria, and fled to Denmark when the Nazis took power in the early 1930’s. I was the physicist who interpreted the work of Otto Hahn and Fritz Straussman in I worked with my nephew, Otto Frisch, and concluded that neutrons actually cleaved the nucleus of an atom of uranium into two or more fragments. This was never suspected. I also coined the phrase “NUCLEAR FISSION”. After World War II I moved to the U.S.

CHAPTER 3LABORATORY CHEMISTRY30 n Beta decay CHANGES IN THE NUCLEUS

CHAPTER 3LABORATORY CHEMISTRY31 CHANGES IN THE NUCLEUS n Gamma decay

CHAPTER 3LABORATORY CHEMISTRY32 CHANGES IN THE NUCLEUS n WHAT CHANGES ACCOMPANY A NUCLEAR REACTION? n DEFINE RADIOACTIVITY. n IS ALL RADIOACTIVITY COMPOSED OF PARTICLES ? n DESCRIBE THE FORCE THAT HOLDS THE NUCLEUS TOGETHER.