Ionization versus Dissociation

1. Ionization versus Dissociation

2. Ionization • To remove a negative charge from a positive charge. • The process of separating electrons from protons is called ionization.

3. Dissociation • Some very similar to ionization that happens to solids. When the ions in a crystal lattice are separated, the process is called dissociation. Example: sodium chloride in water. • Dissociation occurs because of solvation, which requires interaction of similarly electrical properties.

4. Differences between Ionization and dissociation • Ionization, the force comes from within the atom. • Dissociation, the force comes from outside the atom and is the interaction between two or more compounds.

5. Ionic Compounds • Ionization takes place to form solid ionic crystals. Example: Sodium Chloride (Table salt) • Positive sodium ions and negative chloride ions • Ionic crystals can then interact with water molecules to dissociate. • Resulting in a solution that conducts electricity.

6. Microscopic Representation of Ionization • Energy must be added to the neutral atom to remove an electron from a proton. • The amount of energy depends on the type of atom.

7. Ionization is unique to the type of atom • Each element has a characteristic ionization energy. Example: Chlorine is 2.5 times greater than that for sodium.

8. Importance in Understanding Ionization and Dissociation • Together these factors help explain important macroscopic properties. • Solubility • Hardness • Conductivity

9. Electronegativity • Covalent Bonds: Bonding between atoms of similar electrical properties. • Ionization is one way to quantify the electrical properties. • Electronegativity is another way.

10. Electronegativity • When two atoms of the same element bond they form covalent molecules. • Covalent because they share electrons • When two atoms of different element form covalent bonds, the sharing might not be equal.

11. Why don’t some atoms share equally? • Atomic Structure • Some atoms are better at attracting electrons than others. • The ability to attract electrons is known as electronegativity.

12. Linus Pauling • An American chemist created a scale for electronegativity. • He assigned Florine an arbitrary value of 4. • Florine is the most electronegative atom because it is able to attract electrons better than any other element. • Electronegativity values for other elements where created based on a comparison to florine

13. Electronegativity • Can indicate the type of bond that will form. • HOW? • Think Tug-of-War Two same or different atoms One or more electrons

14. Atoms of the Same Strength (Covalent) • There is no winner. • The two atoms share the electrons equally with each other. Two atoms of similar strength One or more electrons

15. Atoms of Somewhat Different Strengths (Polar Covalent) • One atoms pulls the rope more than the other, neither wins. • More rope is to one side of the line Two somewhat different strengths One or more electrons

16. A Polar Covalent Bond • Results in a molecule that has regions of positive charge and regions of negative charge.

17. Atoms that have drastically different values • The atom with greater electronegativity will win. • Electron transfers from atom with low electronegativity to an atom with high electronegativity. • Ions are formed.

18. Atoms that have drastically different values • The attraction between the two oppositely charged ions is called an Ionic Bond High electronegativity Low electronegativity One or more electrons

19. Indicating the bond type

20. Molecule vs Compound • Both terms mean the same concept. • Molecule is the smallest unit of a covalently bonded compound. • Molecules are covalently bonded atoms • Ionic Compounds • Formed by ionic bonding

21. Assignment • Write in your Planner or Table of contents! • I’ll be around to check before class is out. • Page 135-139 • Reflect and Connect #1-4 • Due next class period