Recording-2025-03-05T19:04:56.654Z

Iron Ions and Oxides

• Iron Oxide: Commonly known as rust (chemical formula is Fe2O3).

• Iron Charges:

  • Iron can exist in multiple oxidation states, primarily +2 (iron(II)) and +3 (iron(III)).

  • The discussion focuses on Fe3+, indicating iron in the +3 oxidation state.

Chemical Formula Formation

• To determine the formula, understand the charge of oxygen: O2-.

• Balancing charges:

  • The least common multiple of 3 (iron) and 2 (oxygen) is 6.

  • Thus, require 2 iron (6+) and 3 oxygen (6-), resulting in the formula Fe2O3.

• When indicating charges in parentheses, avoid using this with certain elements (e.g., calcium), as it does not belong to d-block or f-block elements.

Ions and Polyatomic Ions

• Monatomic Ions: Positively or negatively charged single atoms (e.g., Na+, Cl-).

• Polyatomic Ions: Combinations of atoms that act as single ions (e.g., hydroxide, OH-).

  • Example: Hydroxide ion (OH-) is an oxygen attached to hydrogen with a negative charge.

Forming Compounds with Polyatomic Ions

• When combining ions, charge balance is crucial. For example:

  • To balance Ca2+ (calcium) with OH- (hydroxide), 2 hydroxide ions are needed(Ca(OH)2).

• Naming Rule: Include the ion's name, indicating how many are present using parentheses.

  • Example: Iron(III) hydroxide: Written as Fe(OH)3, to show 3 hydroxide for balancing with 3+ charge on iron.

Memorization of Common Ions

• It's essential to memorize some polyatomic ions for naming and chemical reactions.

  • Important ions:

    • Cation: Ammonium (NH4+).

    • Anions: Hydroxide (OH-), Cyanide (CN-).

• Common oxoanions:

  • One Oxoanion: Carbonate (CO3^2-), Phosphate (PO4^3-).

  • Two Oxoanions: Nitrite (NO2-), Nitrate (NO3-), Sulfite (SO3^2-).

Oxoanions with Varying Oxygen Counts

• For ions such as nitrogen:

  • Nitrite (NO2-) vs Nitrate (NO3-): Both are -1 but differ in oxygen counts.

• Ion nomenclature:

  • Naming rules depend on the number of oxygens, e.g., ( -ite ) for fewer (nitrite, NO2-) and ( -ate ) for more (nitrate, NO3-).

  • Chlorine oxoanions follow similar logic: hypochlorite (ClO-), chlorite (ClO2-), chlorate (ClO3-), perchlorate (ClO4-).

Stability and Use of Ions

• Some ions are more stable and commonly found in nature (e.g., hypochlorite in bleach).

• Polyatomic ions can also engage with hydrogen ions (H+), forming variations (e.g., hydrogen carbonate from carbonate).

  • Example: Adding H+ to carbonate (CO3^2-) forms hydrogen carbonate (HCO3-).

  • Naming hydrogen ions follows the same structure where H adds a +1 charge, decreasing total ion charge.

Examples of Charge Balancing

• Example with dihydrogen phosphate (H2PO4-): To balance with a divalent cation like calcium, you would require three such phosphate ions for total charge balance in the compound.