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1.2 atomic structure

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Martin Brown

The document summarizes atomic structure and the development of atomic theory. It discusses key scientists and experiments that led to discoveries such as electrons, protons, neutrons, and the nuclear model of the atom. These include Thomson's work on cathode rays, Rutherford's gold foil experiment, and Chadwick's discovery of the neutron. The document also covers atomic number, mass number, isotopes, relative atomic mass, and how mass spectrometry is used to determine relative atomic masses.

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1.2 Atomic Structure (Time needed: 6 class periods)
Learning outcomes • Matter is composed of particles, which may be atoms, molecules or ions. • Atoms. Minute size of atoms. • Law of conservation of mass.
DIFFUSION- evidence for the existence of small particles • SPREADING OUT OF GASES • COLOUR OF INK SREADING OUT WHEN MIXED WITH WATER • HYDROGEN CHLORIDE AND AMMONIA SOLUTION
AMMONIUM CHLORIDE
law of conservation of mass/matter •The law of conservation of mass/matter, also known as law of mass/matter conservation says that the mass of a closed system will remain constant, regardless of the processes acting inside the system. •Matter cannot be created/destroyed, although it may be rearranged. •For any chemical process in a closed system, the mass of the reactants must equal the mass of the products.
1.2 atomic structure
1.2 atomic structure
Learning Outcomes •Very brief outline of the historical development of atomic theory (outline principles only; mathematical treatment not required): Dalton: atomic theory; •Crookes: vacuum tubes, cathode rays; •Stoney: naming of the electron; •Thomson: negative charge of the electron; e/m for electrons (experimental details not required); •Millikan: magnitude of charge of electrons as shown by oil drop experiment (experimental details not required); •Rutherford: discovery of the nucleus as shown by the α−particle scattering experiment; •discovery of protons in nuclei of various atoms; •Bohr: model of the atom; •Chadwick: discovery of the neutron.
HISTORY OF THE ATOM • GREEKS – MATTER MADE OF TINY INDIVISIBLE PARTICLES
DALTON 1766-1844 • ALL MATTER MADE OF SMALL PARTICLES CALLED ATOMS • ATOMS ARE INDIVISIBLE • ATOMS CANNOT BE CREATED OR DESTROYED
DISCOVERY OF THE ELECTRON • CROOKES CONDUCTED EXPERIMENTS WITH A GLASS TUBE
CROOKES TUBE
CROOKES TUBES • CATHODE CONNECTED TO NEGATIVE ELECTRODE • ANODE CONNECTED TO THE POSITIVE ELECTRODE • CNAP
VACUUM TUBES • GAS AT LOW PRESSURE • ELECTRIC CURRENT PASSED THROUGH • RADIATION CAME FROM THE END OF THE TUBE CONNECTED TO THE NEGATIVE(CATHODE) END OF THE BATTERY • CATHODE RAYS
TUBES
CROOKES PADDLE TUBE
CATHODE RAYS • • • • CAST SHADOWS CAUSE GLASS TO GLOW TURN A PADDLE WHEEL RAYS ARE MADE OF PARTICLES
JJ THOMPSON • HOLE IN ANODE TO ALLOW BEAM OF RAYS TO PASS THROUGH. • BEAM COULD BE DEFLECTED BY ELECTRIC PLATES. • THEREFORE BEAM IS MADE OF NEGATIVE PARTICLES.
JJ THOMPSONS APPARATUS
JJ THOMPSON • USED A MAGNETIC FIELD FROM AN ELECTROMAGNET TO DEFLECT THE ELECTRONS • CALCULATED THE RATIO OF CHARGE TO MASS FOR ELECTRON
GEORGE STONEY • NAMED PARTICLES ELECTRONS
ROBERT MILLIKAN • FAMOUS OIL-DROP EXPERIMENT • IT MEASURED THE CHARGE ON THE ELECTRON • X-RAYS IONISED AIR MOLECULES BY STRIPING ELECTRONS OFF THEIR ATOMS. • OIL DROPLETS PICKED UP ELECTRONS BECAME NEGATIVE • INCREASED THE + CHARGE UNTIL THE DROPLET HOVERED. • TOOK MEASUREMENTS AND CALCULATED THE CHARGE ON THE ELECTRON.
ROBERT MILLIKAN
ROBERT MILLIKAN
THOMPSON’S ATOM • ATOM A SPHERE OF POSITIVE CHARGES WITH NEGATIVE ELECTONS EMBEDDED
ERNEST RUTHERFORD • FIRED THIN ALPHA PARTICLES AT A TIN GOLD FOIL • THOMPSONS PLUM PUDDING MODEL PREDICTED THAT THEY WOULD PASS THRU’ WITH LITTLE DEFLECTION
RUTHERFORD’S EXPT •
RUTHERFORD’S EXPT
EXPECTED RESULT • ALPHA PARTICLES SHOULD PASS THROUGH WITH LITTLE DEFLECTION + ++
ACTUAL RESULT • MOST PASS THROUGH UNDEFLECTED • SOME BOUNCED RIGHT BACK!
EXPLANATION • HARD DENSE CORE OF POSITIVE MATTER IN THE CENTER OF EACH ATOM-NUCLEUS • ATOMS ARE MOSTLY EMPTY SPACE.
THE PROTON • RUTHERFORD CONTINUED TO BOMBARD DIFFERENT ELEMENTS SUCH AS NITROGEN AND OXYGEN • SMALL POSITIVE PARTICLES WERE GIVEN OFF-- PROTONS
THE NEUTRON • JAMES CHADWICK BOMBARDED BERYLLIUM WITH ALPHA PARTICLES. • SMALL PARTICLES WERE GIVEN OFF WHICH WERE NEUTRAL AND HAD THE SAME MASS AS THE PROTON—THE NEUTRON.
1.2 atomic structure
Bohr’s atom • Electrons travel in orbits around the nucleus
1.2 atomic structure
Learning Outcomes • Properties of electrons, protons and neutrons (relative mass, relative charge, location within atom).
Proton • Protons are positively charged particles found within atomic nucleus
1.2 atomic structure
1.2 atomic structure
Learning Outcomes Atomic number (Z ), mass number (A), isotopes; hydrogen and carbon as examples of isotopes. Relative atomic mass (A r). The 12C scale for relative atomic masses.
Atomic number • Also called proton number, this is the number of protons the atom has
1.2 atomic structure
1.2 atomic structure
Atomic number • Also called proton number, this is the number of protons the atom has
The Number of Electrons • Atoms must have equal numbers of protons and electrons. In our example, an atom of krypton must contain 36 electrons since it contains 36 protons.
Mass number •Mass Number = (Number of Protons) + (Number of Neutrons)
Isotope • Atoms that have the same number of protons but different numbers of neutrons are called isotopes
1.2 atomic structure
Hydrogen isotopes • The element hydrogen for example, has three commonly known isotopes: protium, deuterium and tritium
Deuterium •an atom of deuterium consists of one proton one neutron and one electron
Tritium • An atom of tritium consists of one proton two neutrons and one electrons
1.2 atomic structure
Relative Atomic Mass • The relative atomic mass of an element the mass of one of the element's atoms -- relative to the mass of an atom of Carbon 12,
Learning Outcomes • Calculation of approximate relative atomic masses from abundance of isotopes of given mass number (e.g. Calculation of approximate relative atomic mass of chlorine).
Chlorine •Chlorine-35 and Chlorine-37 are both isotopes of chlorine
Relative mass of chlorine • Chlorine consists of roughly 75% Chlorine-35 and roughly 25% Chlorine-37. We take an average of the two figures The relative atomic mass of chlorine is usually quoted as 35.5.
1.2 atomic structure
Learning outcomes • Use of the mass spectrometer in determining relative atomic mass. • Fundamental processes that occur in a mass spectrometer: • vaporisation of substance, • production of positive ions, • acceleration, separation, • detection (mathematical • treatment excluded).
THE MASS SPECTROMETER • Atoms can be deflected by magnetic fields - provided the atom is first turned into an ion.
Stage 1: Ionisation • The atom is ionised by knocking one or more electrons off to give a positive ion.
Stage 2: Acceleration • The ions are accelerated so that they all have the same kinetic energy.
Stage 3: Deflection • The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected.
Stage 4: Detection • The beam of ions passing through the machine is detected electrically.
1.2 atomic structure
1.2 atomic structure

More Related Content

1.2 atomic structure

  • 1. 1.2 Atomic Structure (Time needed: 6 class periods)
  • 2. Learning outcomes • Matter is composed of particles, which may be atoms, molecules or ions. • Atoms. Minute size of atoms. • Law of conservation of mass.
  • 3. DIFFUSION- evidence for the existence of small particles • SPREADING OUT OF GASES • COLOUR OF INK SREADING OUT WHEN MIXED WITH WATER • HYDROGEN CHLORIDE AND AMMONIA SOLUTION
  • 5. law of conservation of mass/matter •The law of conservation of mass/matter, also known as law of mass/matter conservation says that the mass of a closed system will remain constant, regardless of the processes acting inside the system. •Matter cannot be created/destroyed, although it may be rearranged. •For any chemical process in a closed system, the mass of the reactants must equal the mass of the products.
  • 8. Learning Outcomes •Very brief outline of the historical development of atomic theory (outline principles only; mathematical treatment not required): Dalton: atomic theory; •Crookes: vacuum tubes, cathode rays; •Stoney: naming of the electron; •Thomson: negative charge of the electron; e/m for electrons (experimental details not required); •Millikan: magnitude of charge of electrons as shown by oil drop experiment (experimental details not required); •Rutherford: discovery of the nucleus as shown by the α−particle scattering experiment; •discovery of protons in nuclei of various atoms; •Bohr: model of the atom; •Chadwick: discovery of the neutron.
  • 9. HISTORY OF THE ATOM • GREEKS – MATTER MADE OF TINY INDIVISIBLE PARTICLES
  • 10. DALTON 1766-1844 • ALL MATTER MADE OF SMALL PARTICLES CALLED ATOMS • ATOMS ARE INDIVISIBLE • ATOMS CANNOT BE CREATED OR DESTROYED
  • 11. DISCOVERY OF THE ELECTRON • CROOKES CONDUCTED EXPERIMENTS WITH A GLASS TUBE
  • 13. CROOKES TUBES • CATHODE CONNECTED TO NEGATIVE ELECTRODE • ANODE CONNECTED TO THE POSITIVE ELECTRODE • CNAP
  • 14. VACUUM TUBES • GAS AT LOW PRESSURE • ELECTRIC CURRENT PASSED THROUGH • RADIATION CAME FROM THE END OF THE TUBE CONNECTED TO THE NEGATIVE(CATHODE) END OF THE BATTERY • CATHODE RAYS
  • 15. TUBES
  • 17. CATHODE RAYS • • • • CAST SHADOWS CAUSE GLASS TO GLOW TURN A PADDLE WHEEL RAYS ARE MADE OF PARTICLES
  • 18. JJ THOMPSON • HOLE IN ANODE TO ALLOW BEAM OF RAYS TO PASS THROUGH. • BEAM COULD BE DEFLECTED BY ELECTRIC PLATES. • THEREFORE BEAM IS MADE OF NEGATIVE PARTICLES.
  • 20. JJ THOMPSON • USED A MAGNETIC FIELD FROM AN ELECTROMAGNET TO DEFLECT THE ELECTRONS • CALCULATED THE RATIO OF CHARGE TO MASS FOR ELECTRON
  • 21. GEORGE STONEY • NAMED PARTICLES ELECTRONS
  • 22. ROBERT MILLIKAN • FAMOUS OIL-DROP EXPERIMENT • IT MEASURED THE CHARGE ON THE ELECTRON • X-RAYS IONISED AIR MOLECULES BY STRIPING ELECTRONS OFF THEIR ATOMS. • OIL DROPLETS PICKED UP ELECTRONS BECAME NEGATIVE • INCREASED THE + CHARGE UNTIL THE DROPLET HOVERED. • TOOK MEASUREMENTS AND CALCULATED THE CHARGE ON THE ELECTRON.
  • 25. THOMPSON’S ATOM • ATOM A SPHERE OF POSITIVE CHARGES WITH NEGATIVE ELECTONS EMBEDDED
  • 26. ERNEST RUTHERFORD • FIRED THIN ALPHA PARTICLES AT A TIN GOLD FOIL • THOMPSONS PLUM PUDDING MODEL PREDICTED THAT THEY WOULD PASS THRU’ WITH LITTLE DEFLECTION
  • 29. EXPECTED RESULT • ALPHA PARTICLES SHOULD PASS THROUGH WITH LITTLE DEFLECTION + ++
  • 30. ACTUAL RESULT • MOST PASS THROUGH UNDEFLECTED • SOME BOUNCED RIGHT BACK!
  • 31. EXPLANATION • HARD DENSE CORE OF POSITIVE MATTER IN THE CENTER OF EACH ATOM-NUCLEUS • ATOMS ARE MOSTLY EMPTY SPACE.
  • 32. THE PROTON • RUTHERFORD CONTINUED TO BOMBARD DIFFERENT ELEMENTS SUCH AS NITROGEN AND OXYGEN • SMALL POSITIVE PARTICLES WERE GIVEN OFF-- PROTONS
  • 33. THE NEUTRON • JAMES CHADWICK BOMBARDED BERYLLIUM WITH ALPHA PARTICLES. • SMALL PARTICLES WERE GIVEN OFF WHICH WERE NEUTRAL AND HAD THE SAME MASS AS THE PROTON—THE NEUTRON.
  • 35. Bohr’s atom • Electrons travel in orbits around the nucleus
  • 37. Learning Outcomes • Properties of electrons, protons and neutrons (relative mass, relative charge, location within atom).
  • 41. Learning Outcomes Atomic number (Z ), mass number (A), isotopes; hydrogen and carbon as examples of isotopes. Relative atomic mass (A r). The 12C scale for relative atomic masses.
  • 42. Atomic number • Also called proton number, this is the number of protons the atom has
  • 45. Atomic number • Also called proton number, this is the number of protons the atom has
  • 46. The Number of Electrons • Atoms must have equal numbers of protons and electrons. In our example, an atom of krypton must contain 36 electrons since it contains 36 protons.
  • 47. Mass number •Mass Number = (Number of Protons) + (Number of Neutrons)
  • 48. Isotope • Atoms that have the same number of protons but different numbers of neutrons are called isotopes
  • 50. Hydrogen isotopes • The element hydrogen for example, has three commonly known isotopes: protium, deuterium and tritium
  • 51. Deuterium •an atom of deuterium consists of one proton one neutron and one electron
  • 52. Tritium • An atom of tritium consists of one proton two neutrons and one electrons
  • 54. Relative Atomic Mass • The relative atomic mass of an element the mass of one of the element's atoms -- relative to the mass of an atom of Carbon 12,
  • 55. Learning Outcomes • Calculation of approximate relative atomic masses from abundance of isotopes of given mass number (e.g. Calculation of approximate relative atomic mass of chlorine).
  • 56. Chlorine •Chlorine-35 and Chlorine-37 are both isotopes of chlorine
  • 57. Relative mass of chlorine • Chlorine consists of roughly 75% Chlorine-35 and roughly 25% Chlorine-37. We take an average of the two figures The relative atomic mass of chlorine is usually quoted as 35.5.
  • 59. Learning outcomes • Use of the mass spectrometer in determining relative atomic mass. • Fundamental processes that occur in a mass spectrometer: • vaporisation of substance, • production of positive ions, • acceleration, separation, • detection (mathematical • treatment excluded).
  • 60. THE MASS SPECTROMETER • Atoms can be deflected by magnetic fields - provided the atom is first turned into an ion.
  • 61. Stage 1: Ionisation • The atom is ionised by knocking one or more electrons off to give a positive ion.
  • 62. Stage 2: Acceleration • The ions are accelerated so that they all have the same kinetic energy.
  • 63. Stage 3: Deflection • The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected.
  • 64. Stage 4: Detection • The beam of ions passing through the machine is detected electrically.