Chemistry Unit 1

Chemistry Unit 1

1. Mass Number = Number of Protons + Neutrons (in the nucleus/atom)

2. Relative Atomic Mass = The mean mass of an atom of an element compared to one twelfth the mass of a 12C atom.

3. The first ionisation energy is the enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge

   • The second ionisation energy is the enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge
     • Ti+ (g) -->
       Ti2+ (g) + e-
   • X(g)
     --> X+ (g) + e-
   • 1.The attraction of the nucleus (The more protons in the nucleus the greater the attraction)
   • 2. The distance of the electrons from the nucleus (The bigger the atom the further the outer electrons are from the nucleus and the weaker the attraction to the nucleus)
   • 3. Shielding of the attraction of the nucleus (An electron in an outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)

4. Emperical Formula: the simplest whole number ratio of atoms of each element in a compound

5. Covalent Bond: a shared pair of electrons

6. Dative Covalent Bond: A covalent bond in which the shared pair of electrons are provided by just one of the bonded atoms

7. Electronegativity: The power of an atom to withdraw electron density from a covalent bond

8. Structural Isomerism: Compounds which have the same molecular formula but a different structural formula/displayed formula

9. Cracking: A process used by the petroleum industry to produce shorter alkanes and alkenes from longer alkanes

10. Ideal Gas Equation: pV=nRT

11. No. of moles = Mass/Mr

12. Concentration = No. of moles/Volume

13. Atom Economy = (mass desired product / mass all reactants)x100

14. % Yield = (Actual yield / Theoretical yield)x100

15. Mass Spectrometry:

    • Step 1) Ionisation •Sample is dissolved in a polar solvent •A high voltage is applied to sample •The particles lose an electron ( or more) •Forming positive ions with different charges E.g. Ti
      Ti+ + e–
      • Step 2) Acceleration •Positive ions are accelerated by an electric field •To a constant kinetic energy
        • Step 3) Deflection •The positive ions with smaller m/z values will have the same kinetic energy as those with larger m/z and will move faster. •The heavier particles take longer to move through the drift area. •The ions are distinguished by different flight times
          • Step 4) Detection •The ions reach the detector and generate a small current, which is fed to a computer for analysis. The current is produced by electrons transferring from the detector to the positive ions. The size of the current is proportional to the abundance of the species