Nomenclature = Naming and writing of compounds

Oxidation Numbers – the # of e- lost, gained or shared by an element or a polyatomic ion when forming a compound… used for formula writing!

  • Polyatomic ions – a group of atoms that act as one ion (keep them together!)
  • Oxidation number of a polyatomic ion is the charge of the ion
  • Polyatomic ion sheet is arranged as such
  • Common examples
  • NH41+ - ammonia, found in windex
  • OH1- - found in cleaners like drano, nair, deordorant
  • C2H3O21- - found in vinegar
  • NO31- - found in fertilizer
  • CO32- - found in antacids
  • PO43- - found in fertilizer, some soft drinks
  • Non metals gain e-‘s an have negative oxidation #’s
  • Metals lose e-‘s and have positive oxidation #’s
  • Most common oxidation #’s by group #

Group 1 / +1 / Group 5 / -3
Group 2 / +2 / Group 6 / -2
Group 3 / +3 / Group 7 / -1
Group 4 / ±4 / Group 8 / 0

Oxidation rules for finding oxidation #’s

  • Hydrogen is Almost ALWAYS 1+ unless it is the exception below
  • Exception: 1- when bonded with Alkali metals (NaH, KH, LiH, etc.)
  • Oxygen is Almost ALWAYS 2-unless it is the exception below
  • Exception: 1- when bonded as peroxide (H2O2)
  • Group 1 – Na, K, Li is ALWAYS 1+
  • Group 2 – Mg, Ca, Be is ALWAYS 2+
  • Group 7 – F, Cl, I, Br is ALWAYS 1-
  • Elements in their elemental state always have an oxid’n # of 0
  • Na oxid # = 0
  • Cu oxid # = 0
  • S oxid # = 0
  • Charged elements have the oxid’n # = the charge in the upper right hand corner.
  • Na1+oxid # = 1+
  • Cu2+oxid # = 2+
  • S2-oxid # = 2-
  • All other elements you may have to solve for given the information above (called oxid’n numbers backwards)
  • Example – K2SO4 (what is the oxidation number for each element?)
  • K = 1+ (rule stated above)
  • O = 2- (rule stated above)
  • S = ? (many options on the PT so solve)

(create an algebraic equation keeping in mind the # of each element. The eq’n is equal to what is in the upper right hand corner. If there is nothing there, it is equal to 0)

K2SO4

(2 x +1) + (1x S) + (4x -2) = 0

2 + 1 x S + -8 = 0

1 x S = 8-2

S= 6+

You try!

  • HCO31-, solve for each elements oxid’n #’s

Formula Writing

Does it start with a nonmetal and only have nonmetals?

  • You will need to know the number of each element to write the formula. Mono is not used on the first element.
  • Prefixes will tell you the number of each element (on the back of your poly ion sheet)
  • Example
  • 1 carbon 2 oxygen becomes CO2 (carbon dioxide)
  • If it starts with an H it is an acid and has its own set of name and rules! (see back of poly ion sheet)

1 mono- / 6 hexa-
2 di- / 7 hepta-
3 tri- / 8 octa-
4 tetra- / 9 nona-
5 penta- / 10 deca-

Does it start with a metal?

  • Determine the oxidation number of each element and its symbol
  • If the element is a metal with more than one oxidation number (d block, Pb, Sn, etc.) you will need to choose one unless you are told one. (example Cu 2+, Mo7+)
  • Metal groups (without more than one oxid’n #)
  • Group 1 = 1+
  • Group 2 = 2+
  • Groups with nonmetals use the most common oxid # for the group
  • Group 7 = 1-
  • Polyatomic ions use the charge in the upper right hand corner
  • Always write the element with positive oxid’n # first. Cross the oxid’n #’s and write them as subscripts. 1 is implied and never written!!!!!!
  • Example – Na1+ and S2- becomes Na2S
  • Cu2+ and P3- becomes Cu3P2
  • Crossing charges actually balances the positive and negative charges making the molecule neutral
  • If you have more than one polyatomic ion, you will need to include parentheses.

Mg2+ and OH1- becomes Mg(OH)2

Li+ and OH- becomes LiOH

  • If the superscripts are divisible by the same #, you need to find the smallest whole # ratio. This only applies with formula starts with a metal.
  • Example – Ca2O2 should be written as CaO
  • Example – Mo2O4 should be written as MoO2 (divisible by 2)

Formula naming

  • Starts with a metal (Group 1, 2, Ag, Zn)
  • Metal with a nonmetal
  • Name the metal and then name the nonmetal with changing ending to “-ide”
  • Example – NaCl = Sodium Chloride
  • Example – ZnH2 = Zinc Hydride
  • Metal with a polyatomic ion
  • Name the metal and then name the polyatomic ion from the sheet
  • Example – Na2CO3 = sodium carbonate
  • Example – KC2H3O2 = Potassium acetate
  • Starts with a transition metal (metal with more than one oxid’n # - mostly d block, Sn, Pb, etc)
  • Transition metal with a nonmetal
  • Name the metal and write the oxidation # for the metal in Roman numeral form and then name the nonmetal with changing the ending to “-ide”
  • Example – FeCl3 = Iron(III)Chloride
  • Example – Mo2O7 = molybdenum(VII)Oxide
  • Example – CuO = Copper(II)Oxide
  • You may have to do oxidation numbers backwards to determine the correct roman numeral for the metal.
  • Starts with a nonmetal
  • Nonmetals only in which case you must use prefixes (back of poly ion sheet). Last element will end with “-ide”. Do not use mono for the first element ever!
  • Prefixes are: mono-1, di-2, tri-3, tetra-4, penta-5, hexa-6, hepta-7, octa-8, nona-9, deca-10
  • Example – CO = carbon monoxide
  • Example – N2O5 = dinitrogenpentoxide
  • Starts with a polyatomic ion (only ammonium in this class)
  • Name the polyatomic ion first (ammonium) and then name the second part. The second part can be a nonmetal in which case change the ending to “-ide”. If the 2nd part is a polyatomic ion, name the ion.
  • Example – (NH4)2S = ammonium sulfide
  • Example – NH4NO3 = ammonium nitrate

Naming Acids

Acids break into two parts cation (H30+) and an anion (the negatively charged thing) to become a neutrally charged compound

Binary Acids

  • HCl – Hydrochloric Acid = H+ and Cl-
  • HI – Hydroiodic Acid = H3O+ and I-
  • H2S – ?
  • HF - ?

Called binary acids because they have two elements bonded to one another to fill their outer shells.

Prefix for binary acids – “Hydro”

Ending for binary acids – changing the anion to have an ending of “-ic”

Ternary Acids (oxyacids)

Acids that contain some oxygens in their formula. You will look to the polyatomic ion that is the anion and change the ending from “-ate” or “-ic”

  • H2SO4 – Sulfuric Acid
  • HClO3 – Chloric Acid
  • H3PO4 – Phosphoric Acid
  • H2CO3 – Carbonic Acid
  • HC2H3O2 – Acetic Acid
  • HNO3 – Nitric Acid

The above are parent acids, what happen if we lose or gain oxygen’s?

  • HClO3 – Chloric Acid, If we gain a single O, then it becomes HClO4 (Perchloric Acid)
  • If we lose an single O, then it becomes HClO2 (Chlorous Acid)
  • If we lose two O, then it becomes HClO (Hypochlorous acid)
  • These rules should look familiar to the polyatomic ion naming rules!

Halogen Oxyacid Families

  • Same as the rules above with the chloric acid. We are just applying them to the other halogens. All of them start with O3 as your parent.
  • HBrO4
  • HIO
  • HFO2