Molecules and Compounds Nomenclature

Diatomic Molecules

• Elements that exist as diatomic molecules include Hydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2).

Common Names - Exceptions

• Water: $H_2O$ (steam, ice)
• Ammonia: $NH_3$
• Methane: $CH_4$
• Table salt: $NaCl$
• Table sugar: $C<em>{12}H</em>{22}O_{11}$

Classifying Compounds

• Ionic
• Molecular (covalent)

Binary Compounds

• Contain only 2 elements.
• Compounds containing polyatomic ions.

Binary Compounds

• Metal and nonmetal: Binary Ionic.
• Two nonmetals: Binary Covalent.

Binary Ionic Compounds

• Metal cation and nonmetal anion.
• Metals with one possible charge (A).
• Metals with more than one possible charge (B).
• Determine metal cation’s charge from the anion charge.

Metals with Invariant Charge

• Group IA (1+): $Li^+, Na^+, K^+, Rb^+, Cs^+$
• Group 2A (2+): $Be^{2+}, Mg^{2+}, Ca^{2+}, Sr^{2+}, Ba^{2+}$
• Others: $Al^{3+}$, $Zn^{2+}$, $Ag^+$

Naming Binary Ionic Compounds (Type A)

• Metal cation + nonmetal anion
• Metal listed first in formula & name.
• Metal cation name is the metal name.
• Nonmetal anion ends with -ide.

Naming Binary Ionic Compounds (Type B)

• Same as A, but metal cation name is the metal name followed by a Roman Numeral in parentheses to indicate its charge.
• Exceptions: $Sc^{3+}$, $Ag^+$, $Zn^{2+}$

Compounds with Polyatomic Ions

• Polyatomic ions are charged entities containing more than one atom.
• Name polyatomic compounds without changes.
• Follow rules for A and B.

Binary Compounds of 2 Nonmetals: Molecular (Covalent)

• Name first element in formula, use the full name of the element.
• Name the second element as if it were an anion (end with –ide).
• Use a prefix to indicate the number of atoms.
• Never use mono- on the first element.

Prefixes

• mono – 1
• di – 2
• tri – 3
• tetra – 4
• penta – 5
• hexa – 6
• hepta – 7
• octa – 8
• nona – 9
• deca – 10
• Drop last “a” in the prefix if the name begins with vowel

Acids

• Contain $H^+$ cation and anion.
• Binary acids: $H^+$ cation and a nonmetal anion.
• Oxyacids: $H^+$ cation and a polyatomic anion.

Naming Acids

• Binary Acids: Hydro___ic acid (Drop -gen from hydrogen, drop -ide, use -ic acid).
  • Ex: $HCl$ = hydrochloric acid
• Ternary Acids (oxyacids):
  • -ate ending becomes –ic acid
  • -ite ending becomes –ous acid
  • Ex: $HClO<em>3$ = chloric acid, $HClO</em>2$ = chlorous acid