Final answer:
Lewis structures can be used to determine the formula of ionic compounds by counting the total number of valence electrons and balancing charges to achieve neutrality.
Step-by-step explanation:
Lewis structures can be used to determine the formula of ionic compounds by:
- Counting the total number of valence electrons: We consider the valence electrons of each atom involved in the compound and sum them up. For example, in the ionic compound sodium chloride (NaCl), sodium contributes 1 valence electron and chlorine contributes 7 valence electrons. So, the total number of valence electrons is 8.
- By balancing charges to achieve neutrality: The compounds are formed by transferring electrons from one atom to another, resulting in the formation of positive and negative ions. The Lewis structure will show how the positive and negative charges balance each other to achieve overall neutrality.
Example: Let's consider the Lewis structure of the ionic compound magnesium oxide (MgO). Magnesium contributes 2 valence electrons, and oxygen contributes 6 valence electrons. The Lewis structure will show that magnesium donates 2 electrons to oxygen, resulting in the formation of Mg²⁺ and O²⁻ ions, and the compound is overall neutral.