Ionic Bonding

Learning Objectives

the common properties of ionic compounds (brittleness, hardness, melting point, difference in electrical conductivity in solid and molten liquid states), with reference to the nature of ionic bonding and crystal structure
deduction of the formula and name of an ionic compound from its component ions, including polyatomic ions (NH₄⁺, OH⁻ , NO₃⁻ , HCO₃⁻, CO₃²⁻ , SO₄²⁻ and PO₄³⁻)
the formation of ionic compounds through the transfer of electrons from metals to non-metals, and the writing of ionic compound formulas, including those containing polyatomic ions and transition metal ions
the use of solubility tables to predict and identify precipitation reactions between ions in solution, represented by balanced full and ionic equations including the state symbols: (s), (l), (aq) and (g)

Ionic bonding is an electrostatic attraction between a metal and non-metal.
It involves the transfer of valence electrons (outer shell electrons) between atoms.
The metal will lose electrons to become a positively charged cation. The non-metal will gain these electrons to become a negatively charged anion.
By doing this, both the metal and non metal can achieve a full outer shell of electrons.
These ionic compounds can form strong 3D crystal lattices from the electrostatic attractions between the cations and anions. A very good example is salt (NaCl).

To break apart the ions you need a lot of energy. Therefore ionic compounds require a high melting point.
The electrostatic forces between the ions are so strong in the 3D crystal lattice. Therefore ionic compounds are hard. However when they are hit with a huge force, ionic compounds will shatter meaning they are brittle. This is because once the forces are disrupted, the layers of the lattice will repulse and completely break apart.
When ionic compounds are molten or in water they can conduct electricity. This is because the electrons are free to move and can conduct electricity. Ionic compounds do not conduct electricity in its solid form as the electrons are not free to move in this form.

The first video shows how to find the formula of an ionic compound. The second shows more information about ionic compounds.

Finding Formulas of Ionic Compunds

What is an Ionic Compound

Teacher's Tip:

Using the cross over method to determine ionic compound formulas is a sure fire way to get the formula correct.

Most properties of ionic compounds can be best explained by the strong electrostatic attraction between cation and anion.

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