TO REVIEW

• Dalton's Atomic Theory


  Elements are composed of indivisible particles called atoms which maintain their identity in all physical and chemical changes<|>All atoms of a given element are identical; the atoms of different elements are different and have different properties including masses<|>Atoms of an element are not changed into different types of atoms by chemical reactions; atoms are neither created nor destroyed in chemical reaction<|>Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms
• Atoms are not indestructible. They consist of still smaller particles
• The atoms of one element may differ in mass. They are identical, however, in some basic aspects
• Law of Definite Proportion or Composition


  Compounds have a definite composition, regardless of how the samples were prepared or where they originated
• Law of Conservation of Mass


  During physical or chemical change, the total mass of all substances before and after the change are the same. Atoms are neither created nor destroyed, thus, the total mass remains the same
• Law of Multiple Proportions


  If two elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers
• Atom


  The smallest particle of an element that retains the chemical identity of the element
• Subatomic particles

  • Electron
  • Proton
  • Neutron
• Electron


  A subatomic particle that possesses a negative electrical charge
• Proton


  A subatomic particle that possesses a positive electrical charge
• Neutron


  A subatomic particle that has no charge associated with it, that is, it is neutral
• Nucleus


  The small, dense, positively charged center of an atom where all protons and all neutrons are found
• Nucleon


  Any subatomic particle found in the nucleus of an atom
• Extranuclear region


  Where the electrons move rapidly about the nucleus which accounts for most of the volume of an atom
• Electron cloud


  The volume occupied by the electrons which is negatively charged
• Atomic number


  The number of protons in the nucleus of an atom
• Mass number (A)


  The sum of the number of protons and the number of neutrons in the nucleus of an atom
• Isotopes


  Atoms of an element that have the same number of protons and the same number of electrons but different numbers of neutrons
• Isotopes of Carbon


  • carbon-12
  • carbon-13
  • carbon-14
• Radioactive isotopes (radioactive nuclide)


  Isotopes with unstable nucleus which emit radiation spontaneously
• Some Radioactive Isotopes Used in Radiation Therapy

  • cobalt-60
  • iodine-131
  • phosphorus-32
  • radium-226
  • radon-222
  • yttrium-90
• Abnormal cells are more susceptible to radiation damage than normal cells because abnormal cells divide more frequently
• Radioactive isotopes used in radiation therapy

  • iodine - 123
  • iron - 59
  • phosphorus - 32
  • potassium - 42
  • sodium - 24
  • cobalt - 60
  • iodine - 131
  • phosphorus - 32
  • radium - 226
  • radon - 222
  • yttrium - 90
• Half-life


  The time it takes for a radioactive isotope to decay to half its original amount
• Type of emitter

  gamma<|>beta<|>alpha
• Use in therapy

  • External source of radiation in treatment of cancer
  • Cancer of thyroid
  • Treatment of some types of leukemia and widespread carcinomas
  • Used in implantation cancer therapy
  • Used in treatment of uterine, cervical, oral and bladder cancers
  • Implantation therapy
• Cardiac pacemakers powered by plutonium - 238 can remain in a patient for longer periods than those powered by chemical batteries and the additional surgery required to replace batteries is not needed
• Molecule


  A group of two or more atoms that functions as a unit because the atoms are tightly bound together
• Types of molecules

  • Homoatomic molecule
  • Heteroatomic molecule
• Homoatomic molecule


  Contains atoms that are of the same kind
• Elements that normally exist as diatomic molecules

  • hydrogen (H2)
  • nitrogen (N2)
  • oxygen (O2)
  • fluorine (F2)
  • chlorine (Cl2)
  • bromine (Br2)
  • iodine (I2)
• Heteroatomic molecule


  Contains two or more kinds of atoms
• A molecule is the smallest particle of a compound capable of a stable independent existence
• Ion


  An atom that has a net positive or negative charge
• Cation


  An ion with a net positive charge
• Anion


  An ion whose net charge is negative
• Metals atoms tend to lose electrons to form cations, whereas nonmetal atoms tend to gain electrons to form anions
• Chemical formula


  Used to express the composition of molecules and ionic compounds in terms of chemical symbols
• Types of chemical formulas

  • Molecular formula
  • Empirical formula
  • Structural formula
• Molecular formula


  Shows the exact number of atoms of each element in the smallest unit of a substance