Chapter 3: Atomic Structure

Chapter 3: Atomic Structure

1. How is it made?

   • The only atom with no neutrons is the simplest isotope of Hydrog
   • Most of mass is in the nucleus
     • Proton: Charge +1 Mass 1 Electrons: Charge -1 Mass 1/1836 Neutron: Charge 0 Mass 1
   • Numbers
     • Atomic number= no of protons Mass number = number of protons + neutrons 35        Cl 17     

2. Isotopes

   • Isotopes are atoms with some atomic number but different mass numbers. They contain same number of protons but different numbers of neutrons
   • Example:
     • Isotope            Proton     Neutrons Hydrogen-1       1                0 Hydrogen-2        1                1 Hydrogen-3        1               2   

3. The electrons

   • Same as proton number Carbon- 6 electron Sodium- 11 electrons
   • Shells
     • Electrons exist around the nucleus in different energy levels called electron shells
     • Organised
       • 1st Shell = 2 2nd Shell= 8 3rd Shell = up to 18

4. Relative Atomic Mass

   • Chlorine
     • Chlorine has 2 isotopes: Chlorine-35      Chlorine-37 Total mass of 100 atoms= (75 x 35)+ (25 x 37) = 3550 Average mass= 3550/100  = 35.5 Ar = 35.5

5. Relative formular mass

   • Hydrogen (H2) 1 x 2 = 2  H2O 1 x 2 + 16= 18
   • Involving Crystallisation
     • Hydrated Mg Sulphate  MgSO4. 7H2O - calculate Mr of MgSO4 = 24 + 32 + (4 x 16)= 120 Add 7 x Mr of H2O = 7 x 18= 126 Mr = 120 + 126 = 246

6. The Mole

   • Measure of an amount of substance
     •  1 Mole is the amount that contains 6 x 10 (23)  particles of the substance
   • 6 x 10 (23) = Avagadro Number
     • Sodium Chloride is an ionic compound and therfore doesn't contain molecules
   • Detail +
     • 1 mol of Na contains AN atoms of Sodium 1 mol of H2 has AN molecules of hydrogen 1 mol of NaCl contains AN formulae of Sodium Chloride

7. Calculating mass of 1 mole

   • Ar in grams
     •                   Ar                  Mass H               1                      1g O                16                   16g Na             23                    23g
   • Mr in grams:
     •                      Mr                Mass H2                 1 x 2                2g H2O             2 x 1 + 16        18g

8. Molar Volume of Gas

   • 1 mol has a volume of 24 dm (3) Volume = amount x 24 H     3 mol     3 x 24 = 72 CO2     0.25mol   0.25 x 24 = 6

9. Amount of Gas

   • Amount of gas (moles) = volume/ 24 Methane     225.6 dm   225.6/24= 9.4 mol Oxygen    1200 cm (3) /1000        1.2/ 24 = 0.05 mol