Chemistry Atoms and elements

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Chemistry Atoms and elements
2011-10-23 02:13:15
Chemistry science Atoms

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  1. Isotopes
    Atoms of the element, having the same atomic number but they have different mass number. Most elements are isotopes which is why the mass number is offen a decimal
  2. Valence electrons
    electrons in the outer most shell of an atom that are involved in reactions
  3. Valence Shell
    The outer most shell of an atom that contains the valence electrons
  4. Ions
    Charged atom. Occurs when an atom reactes and loses or gains electrons.
  5. Cations
    positive ion. formed when atoms lose electrons
  6. anions
    negitive ions. formed when atoms gain electrons
  7. Ionic compounds
    When writting ionic compouds the cation comes first and the charges must be balenced. To balence the ionic coumpound we can use the swap and drop method. We drop the charge (written in supersript) so it subscript and swap them arond. The charge is gone when we drop and if it is 1 then becomes nothing
  8. Balencing chemical equations
    First write word equation then chemical equaltion then makesure both side of the arrow have the same number of each atom, if not then add big numbers infront of the compound eg 2K2O
  9. Gen family
    • all the following when written alone have a subsript 2 eg O2
    • These elements: Fluorine, Chlorine, Bromine, Iodine, Astatine, Oxygen, Hydrogen, and Nitrogen
  10. Mixture
    Two or more substances combiened in a way that you can easily separate
  11. Compound
    Two or more elements chemically bonded together in a way that you can not easily separate
  12. Physical change
    To do something to a substance and there is no new product formed and you can get it back to its orginal form eg freezing, or evporating
  13. Chemical change
    To do something to a substance that produces a new substance and it can not be returned to it orginal form, eg burning paper.
  14. Rate of reaction
    speed of a reaction. For a reaction to occur they must collid and must be in the correct alinement, and with enough energy
  15. The Collision Theory
    • All substances are bound to undergo changes when they react. These substances are made of billions of particles which maybe either ions, atoms, or molecules
    • The collision theory states that for any substances to react, their particals must collide with another particals for the sunstance to change. For a collision to be successful, the particals must have sufficient energy and must be in the right alignment
  16. factors effecting RoR
    Temperature, Concentration, Surface area, Catalyst
  17. RoR- temperature
    Temperature is the measure of kinetic energy of the particles a substance. By increasing temperature the reactant particles gain more energy so they move faster, creating more successful collisions, as they have suffcient energy to break existing bonds
  18. RoR - Concentration
    Concentration is the amount of particales in a given volume. The more reacting particle in a substance the more collisions occur and faster th reaction goes
  19. RoR - Surface area
    when soild substance react only the exposed particles can react (ie other particles can only collid with exposed particles) The more surface area exposed the more successful collisions occur
  20. RoR - catalyst
    A catalyst is a substance wich speeds up the RoR by is noty used up durinf the reaction, so it is not a reactant. They reduce the amount of energy it takes to form a successful colision