Electronegativity: The Pull on Electrons
* Definition: Electronegativity is a measure of an atom's ability to attract electrons within a chemical bond.
* Trends: Electronegativity generally increases across a period (from left to right) and decreases down a group on the periodic table.
What Happens When There's a Big Difference
* Stronger Pull: When two atoms with a large difference in electronegativity bond, the atom with higher electronegativity exerts a much stronger pull on the shared electrons.
* Electron Transfer: This strong pull is so significant that the more electronegative atom essentially "steals" the electron(s) from the less electronegative atom.
* Ions: This electron transfer creates ions:
* The atom that gains electrons becomes negatively charged (anion).
* The atom that loses electrons becomes positively charged (cation).
The Result: Ionic Bonds
* Electrostatic Attraction: Opposite charges attract! The strong electrostatic attraction between the positively charged cation and the negatively charged anion creates an ionic bond.
* Formation of Crystals: Ionic compounds typically form crystalline structures where ions are arranged in a regular, repeating pattern to maximize electrostatic attraction.
Example:
Sodium (Na) has a low electronegativity, while chlorine (Cl) has a high electronegativity. When they bond, chlorine pulls the electron from sodium, creating a Na⁺ ion and a Cl⁻ ion. The strong attraction between these ions forms the ionic compound sodium chloride (NaCl), commonly known as table salt.
Key Takeaway: Large differences in electronegativity lead to a complete transfer of electrons, resulting in the formation of ions and the strong electrostatic attraction that defines ionic bonding.
