NAMING COMPOUNDS The chemical formula represents the composition of each molecule. In writing the chemical formula, in almost all cases the element farthest to the left of the periodic table is written first because it is the least electronegative.

NAMING COMPOUNDS So for example the chemical formula of a compound that contains one sulfur atom and six fluorine atoms is SF6. If the two elements are in the same Group or Family, the symbol of the element of that is lower in the group (i.e. heavier & lower electronegativity) is written first e.g. IF3.

Naming Covalent Compounds In naming covalent compounds, the name of the first element in the formula is unchanged. The suffix “-ide” is added to the second element. Often a prefix on the name of the second element indicates the number of the element in the compound SF6 – sulfur hexafluoride P4O10 – tetraphosphorous decoxide CO – carbon monoxide CO2 – carbon dioxide

Naming Covalent Compounds Cont. SF6 – sulfur hexafluoride P4O10 – tetraphosphorous decoxide CO – carbon monoxide CO2 – carbon dioxide Notice that the first element does NOT get a mono- prefix!

Hydrogen Cmpds Example HF - hydrogen fluoride HCl - hydrogen chloride The binary compounds of hydrogen are special cases. They were discovered before a convention was adopted and hence their original names have stayed Water H2O is not called dihydrogen monoxide Hydrogen forms binary compounds with almost all non- metals except the noble gases. Example HF - hydrogen fluoride HCl - hydrogen chloride H2S - hydrogen sulfide

Organic Nomenclature The molecular formulas for compounds containing C and H (called hydrocarbons) are written with C first. Example, CH4, C2H6, etc. Organic molecules (containing C) have a separate nomenclature

BINARY IONIC COMPOUNDS Compounds formed by elements on opposite sides of the periodic table which either give up (left side = metals) or take up electrons (right side = nonmetals). Depending on the atom, there can be an exchange of more than one electron resulting in charges greater than ±1.

Group IA – alkali metals – loose 1 e- to form +1 (Na+) Group II A– alkaline earth metals –loose 2 e- to form +2 (Ca+2) Group III A– loose three e- to form +3 (Al+3) Group IV A– loose four e- to form +4 (Sn+4) Group V A– accept three e- to form –3 (N-3) Group VI A– accept two e- to form –2 (O-2) Group VIIA – accept one e- to form –1 (Cl-1)

Naming BINARY IONIC compounds Cations For Na+, Ca2+, the name of the ion is the same except refer to the ion. So SODIUM ION or SODIUM CATION Anions – suffix – “ide” So Cl- is chloride, Oxygen O2- is OXIDE & S2- is SULFIDE NaCl - sodium chloride CaCl2 - calcium chloride

Naming BINARY IONIC compounds EXAMPLES CONT. BaCl2 barium chloride K2O potassium oxide Mg(OH)2 magnesium hydroxide KNO3 potassium nitrate

Covalent, charged compounds - MOLECULAR IONS Negative Molecular Ions Positive Molecular Ions End the name with “ium” or “onium” NH4+ is ammonium, H3O + is hydronium - NO3 - NITRATE 2- SO4 - SULFATE NO2 - NITRITE 3- PO4 - PHOSPHATE

Transition Elements The transition elements are chemically quite different from the metals in the “A” block, due to differences in electronic configuration For example, Fe can loose two or three electrons to become Fe2+ and Fe3+, respectively.

To identify the charge of Fe in a compound the following nomenclature is used. Fe2+ is iron(II) Fe3+ is iron (III) So iron(III) chloride is FeCl3 An older scheme differentiated between the lower and higher charge by ending the name of the element with “ous” to indicate the lower charge and “ic” for the higher. ferrous chloride => FeCl2 ferric chloride => FeCl3 However, this convention does not indicate the numerical value of the charge.

TERTIARY IONIC COMPOUNDS NAME THE METAL NORMALLY, WITH A ROMAN NUMERAL IF NEEDED FOR A TRANSITION METAL NAME THE APROPRIATE POLYATOMIC ION Au2(Cr2O7)3 Sc4(P2O7)3 Mg (SCN)2 V3(BO3)5 Gold (III) Dichromate Scandium Pyrophosphate Magnesium Thiocyanate Vanadium (V) Borate

Summary of Naming Compounds

NAMING ACIDS Pure substance, hydrogen chloride An acid can be defined as a substance that yields hydrogen ions (H+) when dissolved in water. EXAMPLE: HCl Pure substance, hydrogen chloride Dissolved in water (H+ Cl-), hydrochloric acid An oxoacid is an acid that contains hydrogen, oxygen, and another element. HNO3 nitric acid H2CO3 carbonic acid H2SO4 sulfuric acid

Naming Acids Cont. Name of ion Name of Acid Sulfate = (SO4)-2 Sulfuric Acid = H2SO4 Sulfite = (SO3)-2 Sulfurous Acid = H2SO3 Hyposulfite = (SO2)-2 Doesn’t exist!

Representing Formulas of Covalent & Ionic Bonds

Formula Types: empirical molecular H2O H2O CH2O C6H12O6 O O3 N2H4 NH2 An empirical formula shows the simplest whole-number ratio of the atoms in a substance A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance empirical molecular H2O H2O CH2O C6H12O6 O O3 N2H4 NH2

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