Chapter 3: Atomic Structure

Annotations:

• The only atom with no neutrons is the simplest isotope of Hydrog

1. Most of mass is in the nucleus

   Annotations:

   • Proton: Charge +1 Mass 1 Electrons: Charge -1 Mass 1/1836 Neutron: Charge 0 Mass 1
2. Numbers

   Annotations:

   • Atomic number= no of protons Mass number = number of protons + neutrons 35        Cl 17     

Annotations:

• Isotopes are atoms with some atomic number but different mass numbers. They contain same number of protons but different numbers of neutrons

1. Example:

   Annotations:

   • Isotope            Proton     Neutrons Hydrogen-1       1                0 Hydrogen-2        1                1 Hydrogen-3        1               2   

Annotations:

• Same as proton number Carbon- 6 electron Sodium- 11 electrons

1. Shells

   Annotations:

   • Electrons exist around the nucleus in different energy levels called electron shells
   1. Organised

      Annotations:

      • 1st Shell = 2 2nd Shell= 8 3rd Shell = up to 18

1. Chlorine

   Annotations:

   • 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

Annotations:

• Hydrogen (H2) 1 x 2 = 2  H2O 1 x 2 + 16= 18

1. Involving Crystallisation

   Annotations:

   • 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

1. Measure of an amount of substance

   Annotations:

   •  1 Mole is the amount that contains 6 x 10 (23)  particles of the substance
2. 6 x 10 (23) = Avagadro Number

   Annotations:

   • Sodium Chloride is an ionic compound and therfore doesn't contain molecules
3. Detail +

   Annotations:

   • 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

1. Ar in grams

   Annotations:

   •                   Ar                  Mass H               1                      1g O                16                   16g Na             23                    23g
2. Mr in grams:

   Annotations:

   •                      Mr                Mass H2                 1 x 2                2g H2O             2 x 1 + 16        18g

Annotations:

• 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

Annotations:

• 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