ionic compounds

Formation of Ionic Compounds

  • Reactions between metals and non-metals can be very vigorous.

  • Example: Sodium (Na) + Chlorine (Cl) → Sodium Chloride (NaCl)

    • Produces a lot of heat, is explosive at high temperatures.

  • Products form a three-dimensional lattice structure.

Forming Ions

  • Metal atoms lose electrons, forming positively charged ions (cations).

  • Non-metal atoms gain electrons, forming negatively charged ions (anions).

  • Metals have low electronegativities; non-metals have higher electronegativities allowing them to attract electrons.

  • Octet Rule: Atoms tend to gain or lose electrons to achieve a stable electron configuration similar to noble gases.

    • Example: Na loses 1 electron, Cl gains 1 electron, resulting in Na+ (2,8) and Cl- (2,8,8).

Electron Transfer Diagrams

  • Illustrate the transfer of electrons during ionic bond formation.

    • Sodium and Chlorine:

      • Na (2,8,1) → Na+ (2,8)

      • Cl (2,8,7) + 1 electron → Cl- (2,8,8)

  • Group 17 non-metals like Cl form anions with a charge of 1-.

Example with Lithium and Oxygen

  • Oxygen (O) (2,6) gains 2 electrons from two lithium (Li) atoms, forming O2-.

    • Li (2,1) → Li+ (2)

    • 1 Li loses 1 electron; 2 Li required for 1 O.

Magnesium Compounds

  • Magnesium (Mg) (2,8,2) with Oxygen (O) to form Mg2+ and O2-.

  • Electron transfer: 2 electrons from Mg to O, resulting in a stable lattice.

Writing Equations for Reactions

  • Reaction Example: Lithium and Nitrogen

    • Li (2,1) → Li+ (2)

    • N (2,5) → N3- (2,8)

  • Balanced equation: 3Li + N → 3Li+ + N3-

Ionic Compounds Formulas

  • Formulas must balance positive and negative charges.

Example: Sodium Chloride

  • Na+ (1+) + Cl- (1-) → NaCl (1:1 ratio)

Example: Magnesium Chloride

  • Mg2+ (2+) + 2 Cl- (1-) → MgCl₂ (1:2 ratio)

Rules for Writing Chemical Formulas

  • Positive ion symbol written first.

  • Use subscripts for quantity, omit '1'.

  • Charges not included in formulas.

Complex Ionic Compounds

  • Polyatomic ions consist of multiple atoms acting as a single unit with a specific charge.

  • Example: Carbonate (CO₃²-), Nitrate (NO₃-).

  • If more than one polyatomic ion is needed, use brackets.

    • Example: Mg(NO₃)₂

Transition Metals

  • Some can have variable charges. Indicate with Roman numerals.

    • Example: Iron(II) chloride = FeCl₂, Iron(III) chloride = FeCl₃.

Naming Ionic Compounds

  • Cations name as the metal (e.g., Sodium Ion).

  • Anions named based on element name (e.g., Chlorine → Chloride).

  • Polyatomic anions contain oxygen; names end in -ite or -ate (e.g., Nitrate, Nitrite).