Ionic Compounds

The ations bond to the anions. The attractio nbetween anion and cation is an ionic bond. This forms an ionic compound.

Ionic compounds form repeating layers of ions called a lattice. Different ions create different ionic crystals with different properties.

metal atoms give electrons to nonmetals. We end up with a cation and anion that bond together. Sometimes, when the metal has too many electrons to give to a nonmetal, it will bond with (=>) 2 nonmetals. Eg: Ca⁺² and F^-1 will make CaF₂.

Write ions with charges, The nunmber of charge of the cation becomes the quantity of the anion, and the charge of the anion becomes the quantity of the cation.

Ionic compounds are made of cations (positive ions) and anions (negative ions) bonded together. To write their chemical formulas:

1. Identify the ions
   • Determine the charge of the metal cation and nonmetal anion.
   • Example: \(\ce{Ca^{2+}}\) and \(\ce{F^-}\)
2. Balance the total charge
   • The total positive charge must equal the total negative charge.
   • Use subscripts to indicate the number of each ion needed.
3. Criss-Cross Method
   • Write the cation first, then the anion.
   • Swap the magnitude of charges to become the subscript of the other ion: \[ \ce{Ca^{2+} + F^- -> CaF2} \]
   • Reduce subscripts to the simplest ratio if possible.

Example: Aluminum chloride: \[ \ce{Al^{3+} + Cl^- -> AlCl3} \]

Lewis dot formulas show the valence electrons for each atom and how electrons are transferred to form ions:

1. Write the element symbols
   • Place dots around each symbol to represent valence electrons.
2. Transfer electrons from metal to nonmetal
   • Metals lose electrons to become cations.
   • Nonmetals gain electrons to become anions.
3. Show ions with brackets and charges
   • Indicate cations and anions with square brackets and their charges.
   • Example: Sodium chloride

\[ \ch{[Na]+ [ {\charge{0=\:, 90=\:, 180=\:, 270=\:}{Cl}} ]^-} \]

• The transferred electron is shown moving from the metal to the nonmetal.