1. Notes P.1-2 January 22, 2014

2. Objectives You will be able to: – Define metallic, ionic, and covalent bonds and explain their characteristics – State if two atoms will form a covalent or ionic bond – Write ionic formula units

3. Overview of bonding Chemical bond: mutual electrical attraction between the nuclei and valence electrons of different atoms that binds those atoms together. Why do atoms bond? – Most atoms are more stable when they are bonded than they were as individual atoms

4. Types of chemical bonds: Metallic – sea of electrons – Occur between: between metals Ionic – steal electrons – Occur between: metal—nonmetal Covalent – share electrons – Occur between: nonmetal—nonmetal Covalent or Ionic? – Determined by electronegativity difference

5. Remember: Metallic Character METALS (IN YELLOW) NONMETALS (IN GREEN)

6. Practice Label as ionic, covalent, or metallic: NaF CaBr 2 H2SH2S Al 2 O 3 Cu NO 3 Ionic Covalent Ionic Metallic Covalent

7. METALLIC BONDING – Results from the attraction of nuclei to a “sea of electrons”

8. Sea of Electrons

9. METALLIC BONDING – Why an “electron sea”? Vacant p and d orbitals in metal's outer energy levels overlap, and allow outer electrons to move freely throughout the metal – Valence electrons do not belong to any one atom

10. METALLIC BONDING – Common properties of metals: High melting/boiling points Conduct heat and electricity Have luster (shiny) Ductile/malleable – All thanks to the electron sea!

11. IONIC BONDING Results from the electrical attraction between cations and anions Cation: + Anion: -

12. The resulting ions come together due to electrical attraction (opposites attract)

13. IONIC BONDING Common Properties: Solid crystals at room temperature Very high melting/boiling points (Most) Can dissolve in water Conduct electricity when melted or dissolved

14. Ionic Formula Units The net (total) charge on the compound must equal zero Positive and negative cancel out Hint: Use the criss-cross method

15. Ionic Formula Units EXAMPLES: Na and Cl Na and O Ca and O Ca and Cl Al and O

16. Ionic Formula Units EXAMPLES: Na and Cl  Na + + Cl -  NaCl Na and O  Na + + O 2-  Na 2 O Ca and O Ca and Cl Al and O

17. Na and O Na2O means that: Two sodium cations are needed to balance one oxygen anion.

18. Positive and negative charges must cancel each other out EXAMPLES: Total + Total - Net Na + and Cl -  NaCl 1 1 0 Na + and O 2-  Na 2 O 2 2 0 Ca 2+ and O 2-  CaO 2 2 0 Ca 2+ and Cl -  CaCl 2 2 2 0 Al 3+ and O 2-  Al 2 O 3 6 6 0

19. Crystal Lattice A network of alternating cations and anions

20. Ionic compounds The formula for ionic compounds does not show the exact number of atoms that are bonded together. The formula tells the smallest whole number ratio of atoms that bond.

21. COVALENT BONDING Results from the sharing of electron pairs between two atoms (each has a full valence shell) A covalent compound is called a molecule

22. Each has a full octet

23. COVALENT BONDING Common properties of covalent compounds: Low melting/boiling points Many are liquids or gases at room temp Non-conductors of heat and electricity

24. Can you…? – Define metallic, ionic, and covalent bonds and explain their characteristics? – State if two atoms will form a covalent or ionic bond? – Write ionic formula units? – Homework 6A, Due Friday – Lab on Friday