Chemical Formulas and Nomenclature 

Chemical formulas: represent the number of atoms of each element in a compound

Atom: the base unit of any element, smallest piece of an element that still has the qualities of the element

Ions: charged atoms [see my note “isotopes and ions” for more details]

  • Cation: positively charged atoms/ions (typically metals)
  • Anion: negatively charged atoms/ions (typically nonmetals)

\ See my note “Isotopes and Ions” if you do not understand what these charges mean:

Group 1: 1+ charge

Group 2: 2+ charge

Group 3 - Group 12 (excluding 13, 30, and 47) + 31, 32, 49, 50, 51, 81, 82, 83, 84, 113, 114, 115, 116: transition metals with various charges

Group 18 (excluding the transition metals): no charge

Group 17 (excluding the transition metals): 1- charge

Group 16 (excluding the transition metals): 2- charge

Group 15 (excluding the transition metals): 3- charge

Group 14 (excluding the transition metals): either 4+ or 4- charge

\ Polyatomic Ions: groups of covalently bonded atoms that have a charge [see my note on common polyatomic ions]

Ionic Compound: contain a cation (metal) and an anion (nonmetal)

Molecule: two or more atoms (usually nonmetals) that are covalently bonded

Diatomic molecule: elements that in their natural form are only found in molecules of two atoms. For example: oxygen is only found as O2, you will only find oxygen alone in chemical reactions

  • the 7 diatomic molecules are : H, O, N, Cl, Br, I, F

\ Binary compounds: compounds of only 2 elements (Ex: H2O, CO2)

Binary Type I: Ionic Compound Containing one cation and one anion both with known charges (no transition metals except Al, Zn and Ag)

Binary Type II: Ionic Compound Containing one cation and one anion with the cation being any transition metal except Al, Zn, and Ag

Binary Type III: Covalent Molecular Compound Containing two nonmetals, doesn’t have a charge

Ternary Compounds: compound containing 3 or more elements

\ How to name

Binary type I:

  • “cation” “root of anion” “ide”
  • CaCl2 (1 Calcium + 2 Chlorine) = Calcium Chloride
  • If we see Calcium Chloride written we know that because Calcium has a +2 charge and Chlorine only has a 1- then there must be two Chlorines for the charges to balance out and be neutral (see my note “paper notes on compounds”)

Binary type 2:

  • because the cation is an element than can have various charges, it’s important to mention what the charge this sample of it has
  • FeO (in which the iron has a charge of +2) = Iron (II) Oxide
  • we use the Roman numerals in parentheses to show the charge on the cation

Ternary:

  • if the ternary compound is something like “cation + compound with negative charge” or “compound with positive charge + anion” you name it very similar to a Binary type I or II compound.
  • The first element or compound is just that element/compound’s name (following the rules of marking the charges as shown in Binary type II if needed)
  • If the second element or compound is a compound, then you just add the compound’s name
  • If the second element or compound is an element, then you just add the root of the element’s name + “ide” (like Binary Type I)
  • Na(CO4) [Sodium + Chlorate] = Sodium Chlorate
  • Fe(CO4)3 [Iron (III) + Chlorate] = Iron (III) Chlorate
  • (NH4)Cl [Ammonium + Chlorine] = Ammonium Chloride

Binary type 3:

  • Because binary type 3 compounds are not ionic, they do not have a charge
  • Since we cannot figure out how many of each element there are based on their charges, we use Greek prefixes to note how many of each
  • for example: C2O would be DIcarbon MONoxide
  • we do not use the prefix “mono” if the first element in the compound only has one of it, the “mono” would just be implied (CO2 is Carbon Dioxide, not monocarbon dioxide)

\ Greek Prefixes:

 1. mono  2. di  3. tri  4. tetra  5. penta  6. hexa  7. hepta  8. octa  9. nona

  1. deca

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