Webpage Addendum - Solubility & Oxidation Numbers
02/26/14
Short Subset Solubility Rules:
Cations: Li+, Na+, K+, NH4+ are always soluble
Anions: NO3-, C2H3O2- are always soluble. Anions OH- , CO3 2- , and S 2- are usually insoluble - unless paired with the always soluble cations above.
Assigning Oxidation Numbers to atoms:
1. For a metal (cat) ion, Ox # is the same as the charge on the ion
2. H is always +1 oxidation number in a compound
3. An element by itself (not an ion and not in a compound) has Ox # = zero.
4. pretend to give electrons to the more electronegative element (as much as it wants to get 8 valence electrons; so oxygen wants 2 e- Cl would want 1 e- etc.) The resulting PRETEND charge on that atom becomes its Oxidation #.
5. Figure the Ox # on the other non-metal atom such that all the Ox #s add up to zero for the compound. For a polyatomic ion, the Ox #s add up to the charge on the ion.
(Remember, for molecular compounds, the Ox # IS NOT the charge on the atoms because molecular compounds are not ionic; i.e. no full charges. Oxidation # only shows if the particular atom in a compound has more electrons drawn to it or less compared to if it were just by itself (not in a compound). )
Oxidation Numbers are useful in deciding if the particular atom was oxidized (Ox# increased) or Reduced (Ox # went down) in a chemical reaction.
Some Mnemonics: (Leo the Lion goes Gerrrrrr )
LEO - losing electrons = Oxidation
GER - gaining electrons = Reduction
or "OIL RIG" - Oxidation Is Losing, Reduction Is Gaining (electrons) .
02/26/14
Short Subset Solubility Rules:
Cations: Li+, Na+, K+, NH4+ are always soluble
Anions: NO3-, C2H3O2- are always soluble. Anions OH- , CO3 2- , and S 2- are usually insoluble - unless paired with the always soluble cations above.
Assigning Oxidation Numbers to atoms:
1. For a metal (cat) ion, Ox # is the same as the charge on the ion
2. H is always +1 oxidation number in a compound
3. An element by itself (not an ion and not in a compound) has Ox # = zero.
4. pretend to give electrons to the more electronegative element (as much as it wants to get 8 valence electrons; so oxygen wants 2 e- Cl would want 1 e- etc.) The resulting PRETEND charge on that atom becomes its Oxidation #.
5. Figure the Ox # on the other non-metal atom such that all the Ox #s add up to zero for the compound. For a polyatomic ion, the Ox #s add up to the charge on the ion.
(Remember, for molecular compounds, the Ox # IS NOT the charge on the atoms because molecular compounds are not ionic; i.e. no full charges. Oxidation # only shows if the particular atom in a compound has more electrons drawn to it or less compared to if it were just by itself (not in a compound). )
Oxidation Numbers are useful in deciding if the particular atom was oxidized (Ox# increased) or Reduced (Ox # went down) in a chemical reaction.
Some Mnemonics: (Leo the Lion goes Gerrrrrr )
LEO - losing electrons = Oxidation
GER - gaining electrons = Reduction
or "OIL RIG" - Oxidation Is Losing, Reduction Is Gaining (electrons) .