Chemistry

Chemistry

1. Atomic Structure

   • Protons
     • Charge= +1
     • Relative Mass= 1
   • Neutrons
     • Charge= 0
     • Relative Mass= 1
   • Electrons
     • Charge= -1
     • Relative Mass= 0.0005
   • Isotopes- different forms of the same element. Same number of protons, different number of neutrons.

2. Periodic Table

   • Mendeleev
     • 1834-1907. Published first table in 1869
     • Ordered the Table in order of Relative Atomic Mass
       • Arranged it so that elements with similar properties are in the same columns
     • left gaps for undiscovered elements
     • Switched the order of a few elements
       • Tellurium and Iodine
   • Vertical Columns/Groups
   • Horizontal Periods- increasing atomic (proton) number

3. Solvent-the liquid in which a solute is dissolved to form a solution

4. Solution-the mixture formed when a solute has dissolved in a solvent

5. Solute-substance that dissolves in a liquid to form a solution

6. Soluble- can be dissolved in a liquid

   • Insoluble- cannot be dissolved in a liquid

7. Chromatography

   • Rf value- retardation factor
     • Rf=distance travelled by solute/ distance travelled by solvent
   • First, draw a horizontal line a few cm above the bottom of the chromatography paper using a pencil
     • Choose an ink/some inks and place a dot of it on the line
       • Attach the top of the paper to a pencil
         • (so it stays up on the rim of the cup)
         • Place solvent into a beaker
           • Make sure it is a few cm below the pencil line on the paper
           • Place the paper into the beaker, and leave it in there for the required amount of time
             • Remove the paper from the solvent
               • The inks may or may not have spread
                 • If it did not, then it is insoluble in that solvent

8. Changes of State

   • Heating/cooling curve
     • curved-pure
     • straight-impure
   • Solid ->Melting -> Liquid
   • Liquid -> Evaporating -> Gas
   • Gas -> Condensing -> Liquid
   • Liquid -> Freezing -> Solid
   • Solid -> Sublimation -> Gas
   • Gas -> Deposition -> Solid
   • Solid
     • Not much energy, vibrate in fixed positions
       • Strong forces of attraction between particles
         • Fixed Volume
         • cannot be compressed
       • Regular pattern
   • Liquid
     • A bit more energy, move around, bounce off surfaces
       • Lesser forces of attraction between particles
         • Randomly arranged
   • Gas
     • A lot of energy, move around freely
       • Very little force of attraction between particles
         • Very randomly arranged
         • no fixed volume

9. Atomic Structure

   • Shell: 2, 8, 8, etc.
   • Shells surround the nucleus
     • Protons and neutrons are found in the nucleus
     • number of shells=period number
       • 1913- Bohr discovered that electrons in fixed orbits surround a small, positively charged nucleus
   • Na
     • Sodium
   • 23
     • mass number
   • 11
     • proton/atomic number