Ionic Compounds & Nomenclature

Aluminum and Sulfur Reaction

• Aluminum reacts with sulfur.
• Aluminum's charge is 3+.
• Sulfur's charge is 2-.
• The least common multiple of 3 and 2 is 6.
• To get six charges, you need two aluminum atoms and three sulfur atoms.

Naming Ionic Compounds (Nomenclature)

• Metals react with nonmetals to form ionic compounds.
• A naming system (nomenclature) is needed for these compounds.
• Binary compounds consist of two elements.
• Binary ionic compounds contain a metal and a nonmetal.
• Metals usually have positive charges, and nonmetals have negative charges.

Predictable Metals

• Group 1A, 2A metals have predictable charges.
• Aluminum (Al) and Gallium (Ga) consistently form 3+ ions.
• Boron (B) doesn't typically form ions.
• Indium (In) and Thallium (Tl) can form multiple ions.

Naming Well-Behaved Metals

• For metals with only one common charge, name the metal and the nonmetal with an "ide" ending.
• Example: NaCl is Sodium Chloride.

Nonmetal Naming Conventions

• Nitrogen becomes Nitride.
• Phosphorus becomes Phosphide.
• Arsenic becomes Arsenide.
• Sulfur becomes Sulfide.

Example: Aluminum Bromide

• $AlBr_3$: Aluminum is in group 3A, so it's Al3+.
• Bromine becomes Bromide.

Example: Strontium Nitride

• Strontium (Sr) is in column 2A.

Metals with Multiple Charges

• Most transition metals and some others can form ions with different charges.
• If a metal has multiple possible charges, you can't use the simple naming system.
• Example: Iron can be Fe2+ or Fe3+.

Old Naming System (Not Used Anymore)

• Fe2+ was called Ferrous.
• Fe3+ was called Ferric.
• $Sn^{2+}$ was called Stannous.
• $Sn^{4+}$ was called Stannic.

Naming Metals with Multiple Charges (Modern Approach)

• Metals that are "well-behaved":
  • Group 1A (+1 charge)
  • Group 2A (+2 charge)
  • Silver (Ag, +1 charge)
  • Cadmium (Cd, +2 charge)
  • Zinc (Zn, +2 charge)
  • Aluminum (Al, +3 charge)
  • Gallium (Ga, +3 charge)
• All other metals typically have two common charges.

Determining Charge from Formula

• The overall charge of a neutral compound is zero.
• Example: $Cu_2O$ (Copper Oxide)
  • Oxygen has a charge of -2.
  • The two copper atoms must have a combined charge of +2 to balance the -2 from oxygen.
  • Each copper atom has a charge of +1.

Example: Gold Sulfide

• $Au_2S$: You need two gold atoms to balance the 2- charge of sulfur.

Balancing Charges

• The goal is to make the smallest whole number ratio that balances out to zero.
• Aluminum Oxide: Aluminum is 3+, and oxygen is 2-.
• To balance, you need two aluminum atoms (2 * +3 = +6) and three oxygen atoms (3 * -2 = -6).
• Formula: $Al<em>2O</em>3$

Polyatomic Ions

• Groups of atoms that are bonded together and have an overall charge.
• These are ions, not compounds.
• Example: Ammonium ($NH_4^+$).

Common Polyatomic Ions (Table 4-3, Page 107)

• Learn the name, formula, and charge of each.
• Ammonium: $NH_4^+$
• Nitrate: $NO_3^-$
• Sulfate: $SO_4^{2-}$
• Hydrogen Sulfate: $HSO_4^-$
• Phosphate: $PO_4^{3-}$
• Dihydrogen Phosphate: $H<em>2PO</em>4^-$
• Carbonate: $CO_3^{2-}$
• Hydrogen Carbonate: $HCO_3^-$
• Cyanide: $CN^-$
• Hydroxide: $OH^-$

Forming Compounds with Polyatomic Ions

• Use the same balancing method as with simple ions.
• Example: Sodium Sulfate ($Na<em>2SO</em>4$)
• Example: Magnesium Sulfate ($MgSO_4$)

Chromium(III) Nitrate

• Chromium(III) is $Cr^{3+}$.
• Nitrate is $NO_3^-$.
• To balance, you need three nitrate ions.
• Formula: $Cr(NO<em>3)</em>3$

Iron Sulfate

• Formula: $Fe<em>2(SO</em>4)_3$
• Sulfate has a 2- charge, and there are three of them, for a total of -6.
• To balance, you need +6 from the iron ions.
• With two iron atoms, each must have a +3 charge.

Aluminum Carbonate and Hydrogen Carbonate

• Aluminum is 3+.
• Carbonate is $CO_3^{2-}$.
• Hydrogen Carbonate is $HCO_3^-$.

Manganese(III) Phosphate

• $Mn<em>3(PO</em>4)_2$