Ionic Compounds and Charge Balancing

Oxygen's Charge
- Oxygen carries a charge of $(-2)$
- Defined as a non-metal
- Non-metals gain electrons to form anions (negatively charged ions)
- Oxygen is located at the upper right side of the periodic table's "double bond demarcation line"
- To achieve a stable electron configuration, it aims for a total of eight electrons (octet rule)
- Valence Electrons: Oxygen has 6 valence electrons
  - Needs 2 more electrons to fill its valence shell
Combining Cation and Anion Together
- Goal: Create a neutral compound by balancing the positive and negative charges
- Identify the least common multiple (LCM) of the charges: (3) (from Al³⁺) and (2) (from O²⁻)
  - LCM of 3 and 2 is 6
- Charge Balancing:
- Cation (aluminum) charge: (+3 \rightarrow +6)
- Anion (oxygen) charge: (-2 \rightarrow -6)
- Calculate Quantity of Ions Needed:
  - For aluminum:
  - Each aluminum yields a charge of +3
  - To achieve +6, you need 2 aluminum atoms: (2 \times 3 = 6)
  - For oxygen:
  - Each oxygen yields a charge of -2
  - To achieve -6, you need 3 oxygen atoms: (3 \times -2 = -6)
- Resulting Neutral Compound:
  - The compound formed will be ( ext{Al}2 ext{O}3 )
  - Name: Aluminum oxide
  - Naming convention: First element + second element with -ide suffix

Calcium Chloride:
- Formula: ( ext{CaCl}_2 )
- Name Calcium
- Calcium:
- Atomic symbol: Ca
- Group: Alkaline Earth Metal
- 2 valence electrons in the outer shell
- Calcium loses 2 electrons to form a cation with a charge of +2 (Ca²⁺)
- Chlorine:
- Atomic symbol: Cl
- Has 7 valence electrons
- Gains 1 electron to form an anion with a charge of -1 (Cl⁻)
- Charge Balancing:
- LCM of 2 (Ca) and 1 (Cl) is 2
- Therefore, you need 1 calcium and 2 chlorines
- Final name: Calcium chloride
Sodium Sulfide:
- Formula: ( ext{Na}_2 ext{S} )
- Sodium (Na) is the first element.
- Sulfur (dialing the periodic table) is the second element.
- Since this is a binary compound, name will end with -ide: Sodium sulfide

Naming Transition Metal Compounds:
- Example: Cobalt (Co)
- Cobalt can have multiple oxidation states (e.g., Co²⁺ or Co³⁺)
- Requires a Roman numeral in the name to indicate charge (e.g., cobalt(II) oxide)
Example: Cobalt Oxide
- Formula: ( ext{CoO} )
- Charge on oxygen: (-2)
- Thus, Co must be (+2) for compound to be neutral: Thus name is Cobalt(II) Oxide

Exceptions for Main Group Metals:
- Tin (Sn) and Lead (Pb) require Roman numerals even though they are main group metals
- They exhibit multiple oxidation states similar to transition metals.
Exceptions for Transition Metals with Fixed Charges:
- Zinc (Zn): Always +2
- Cadmium (Cd): Always +2
- Silver (Ag): Always +1

Definition: Ternary compounds consist of three or more elements, including at least one polyatomic ion
Example Structure: ( ext{Barium Sulfate} )
- Barium (Ba²⁺) plus sulfate (SO₄²⁻) leads to successful formulation as BaSO₄
Naming Polyatomic Ions:
- Certain key polyatomic ions need to be memorized:
- Acetate: ( ext{C}2 ext{H}3 ext{O}_2^{-} )
- Hydroxide: ( ext{OH}^- )
- Ammonium: ( ext{NH}_4^{+} )
- Nitrate: ( ext{NO}_3^{-} )
- Phosphate: ( ext{PO}_4^{3-} )
- Carbonate: ( ext{CO}_3^{2-} )

Charge Balancing: Essential in determining the formula of ionic compounds
- Always adjust to ensure a neutral compound by ensuring the sum of positive and negative charges equals zero.
- Usage of Roman Numerals in naming is crucial for transition metals and exceptions.