Chemistry

Chemistry

1. Atoms

   • Atoms are made up of subatomic particles
     • Protons
       • Neutrons
         • Electrons
           • 1/1837 = 0.0005
         • 1
       • 1
       • All of the particles are sub-atomic
   • Nuclei
     • The nucleus contains Protons and Neutrons
   • Mass Number is the Protons + Neutrons added together
     • Atomic Number = Number of protons
       • Number of protons = Number of electrons (unless it is an ion)
     • Mass number = Protons + Neutrons
       • Neutrons can be found by subtracting the atomic # from the mass #

2. Isotops

   • Isotopes are atoms that have the same protons but different amnts of neutrons
     • They have the same chemical properties due to the electron structure
       • But different physical properties due to their masses

3. Shells

   • Shells are a space around the nucleus where the electron orbits
     • K
       • L
         • M
           • N
             • 32
           • 18
         • 8
       • 2
     • Subshells
       • Contain orbitals
         • Orbitals can hold 0, 1 or 2 electrons
           • S
             • P
               • D
                 • F
                   • 14
                 • 10
               • 6
             • 2

4. Periodic Table

   • Across a period
     • Contains periods and groups (also known as families
       • As the period goes across the metallic character decrease while non metallic character increases
       • Atomic size decreases from metals to non metals across a period
       • Reactivity is generall lowest in middle of period and increases toward either end
       • Electronegativity Also know as electron attracting power of an atom, increases from metals to non metals across a period.
   • Down a group
     • Metallic character increases down a group while non metallic character decreases
     • Atomic size increases down a group
   • Areas of the table
     • Alkali Metals (Group 1)
       • React with water to create alkali solutions
       • Low melting and boiling points
     • Alkali earth metals (Group 2)
       • Call earth metals cause they were first extracted from oxides found in earths crust
     • Halogens (Group 17)
       • So reactive they never occur freely in nature
     • Noble/Inert gases (Group 18)
       • Extremely unreactive
     • Metals and Non Metals
       • A diagonal line starting from boron seperates metal and non metals. To the left is metals, to the right is non metals
         • Change from metal to non metal is gradual. Some elements have characteristics of both metals and non metals (Named metalloids)
     • Between groups 2 - 13 are called transition metals
       • Hard metals, usually have high melting and boiling points
     • Period 6 contains 14 elements name lanthanides or rare elements because of their rare occurence in nature
       • Period 7 contains 7 radioactive elements named actinides

5. The Mole

   • Avagadros number
     • 6.02x10^23
       • 6.02x10^23 = 1mol
         • 1/2 mole is 3.01x10^23
   • no. particles = no of moles x av's #
     • n = mole
       • Mr/M = Molar Mass
         • m = grams
   • Percentage composition
     • percentage of each element contributing to the mass
       • Formula mass of element in 1 mol of compound / molar mass of compund * 100
   • Empirical Formula
     • Step 1- Write down the symbols of the elements present
       • Assume that the mass of the sample is 100g and all percentages come grams
         • Convert masses to moles
           • Find the simplest whole number ratio of the atoms dividing all numbers of moles by the smallest number of moles
             • If necessary multiply by a factor to convert all numbers to whole numbers
   • Calculate mass from moles
     • Since n=m/M, then m = n x M
   • Determining the # of atoms present in a sample
     • n x 6.02x10^23
     • Determining the # of moles given # of particles
       • number of molecules / 6.02x10^23
   • Calculating moles from mass
     • mass(grams) / molar mass
   • Calculating mass from # of particles
     • m = n x Mr
   • Calculate molecular formula from empirical formula and RMM (relative molecular mass
     • Take the empirical formula and add the masses of each element
       • Molecular mass / emperical formula mass
         • take the ratio and x emperical formula (e.g if ratio is 6 time emperical formula by 6)
   • Formulae from % compoisition and RMM
     • Calculare the emperical formula
       • Calculate the emperical formula's mass
         • Ca;culate the ratio (molecular mass / emperical formula mass)
           • Therfore molecular formula = ratio x emperical formula

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