Formation of the Ionic Bond: Electrostatic Attraction Between Opposites
Why Do Atoms Form Ions?
Definition
Octet rule
Atoms are driven by their quest for stability, often achieved by attaining a noble gas electron configuration, commonly referred to as the octet rule.
- Metals, with only a few electrons in their outermost shells, tend to lose electrons, forming positively charged ions called cations.
- In contrast, non-metals gain electrons to fill their outer shells, forming negatively charged ions, or anions.
How Ionic Bonds Form
- When a metal and a non-metal interact, the metal atom transfers one or more electrons to the non-metal atom.
- This transfer creates oppositely charged ions, which are held together by electrostatic forces, which is the attraction between positive and negative charges.
- This force is the essence of an ionic bond.
Definition
Ionic bond
An ionic bond is the electrostatic force of attraction between a positively charged metal ion and a negatively charged non-metal ion.
Formation of Sodium Chloride ($ \text{NaCl} $)
- A sodium atom ($ \text{Na} $) loses one electron, becoming a sodium ion ($ \text{Na}^+ $).
- A chlorine atom ($ \text{Cl} $) gains that electron, becoming a chloride ion ($ \text{Cl}^- $).
- The $ \text{Na}^+ $ and $ \text{Cl}^- $ ions are then attracted to each other, forming the ionic compound sodium chloride.
- The strength of an ionic bond depends on the charges of the ions and the distance between them.
- Higher charges and smaller ionic radii result in stronger bonds.
Naming Binary Ionic Compounds: Cation First, Anion Second
- When naming ionic compounds, the cation (positive ion) is always named first, followed by the anion (negative ion).
- The name of the cation is the same as the name of the metal, while the name of the anion is derived from the non-metal with the suffix -ide.
- $ \text{NaCl} $: Sodium chloride
- $ \text{MgO} $: Magnesium oxide
- $ \text{AlN} $: Aluminum nitride
- Do not reverse the naming order.
- Always name the cation first, even though it is written to the left of the anion in the chemical formula.
What is the name of the compound $ \text{CaS} $?
Polyatomic Ions: Groups of Atoms Acting as a Single Ion
- Not all ions are single atoms.
- Some ions consist of multiple atoms bonded together, carrying an overall charge.
- These are called polyatomic ions, and they behave as a single unit in chemical reactions.
Common Polyatomic Ions You Should Know:
- Sulfate: $SO_4^{2-}$ (found in gypsum and detergents)
- Nitrate: $NO_3^-$ (common in fertilizers and explosives)
- Carbonate: $CO_3^{2-}$ (present in limestone and baking soda)
