The atom and redox

The atom and redox

1. Relative mass

   • Relative isotopic mass
     • The mass of one atom of an isotope relative to 1/12th of the mass of carbon-12
   • Relative atomic mass
     • The weighted mean mass of one atom of an element relative to 1/12th of the mass of carbon-12

2. Ionisation energy

   • 1st ionisation energy
     • Energy required to remove one electron from each atom in one mol of gaseous atoms to form one mol of gaseous +1 ions
   • Factors
     • Electron shielding
       • Electrons closer to the nucleus can repel electrons
     • Nuclear charge
       • The higher the charge the stonger the attraction to e- so higher ionisation energy
     • Nuclear distance
       • The further away the electron the weaker pull the nucleus has on it

3. Orbitals

   • S subshell
     • 2e- MAX
     • 1 in every shell
     • circle
   • p subshell
     • 3 orbitals
     • 6e- max
     • Dumbbell shaped
   • d subshell
     • 5 orbitals
     • 10e- MAX
   • Each orbital can hold 1 pair of electrons
   • Shells
     • Shell 1 - 2e-
     • Shell 2 - 8e-
     • Shell 3 - 18e-
     • Shell 4 - 32e-
   • The 4s subshell is filled before the 3d subshell because 4s is at a lower energy level

4. Redox

   • Oxidation is the loss of electrons - charge increases
   • Reduction - Gain of electrons - charge recuced
   • Oxidising agent - element being reduced
   • Reducing agent - the element being oxidised

5. Oxidation numbers rules:

   • 1) Atoms of uncombined elements have an ON of 0
   • 2) Atoms of a group 1 element have an ON of +1
   • 3) Atoms of a group 2 element have an ON of +2
   • 4) Fluorine atoms have ON of -1
   • 5) Oxygen atoms have an ON of -2 except when it is in peroxide then it is -1
   • 6) Hydrogen atoms gave an ON of +1 except when in hydride it is -1