Wednesday November 7, 2012

1. WednesdayNovember 7, 2012 • (Pop Quiz – Ionic Bonds, Octet Rule, Lewis Structures, Salts, and Acids; WS - Covalent Bonding)

2. Bell RingerWednesday, 11-7-12 Identify the following acids as either binary or oxyacids, then name them. Name these salts, then determine the acid and base from which the salts were formed. HCl KBr binary acid potassium bromide hydrochloric acid HBr and KOH H3PO4 MgCl2 magnesium chloride oxyacid HCl and Mg(OH)2 phosphoric acid

3. Announcements Happy November

5. Pop Quiz Ionic Bonds, Octet Rule, Lewis Structures, Salts, and Acids You may use the following reference materials on this Pop Quiz: • your Periodic Table • your Electronegativity/Bonding Character Chart • the Worksheet titled “Properties of Ionic and Covalent Compounds” • the Worksheet titled “Ionic Bonds, The Octet Rule, and Lewis Structures”

6. Covalent Bonding It’s nice to share!

7. Covalent Bondingand Molecular Compounds A molecule is a neutral group of atoms that are held together by covalent bonds. A molecule may consist of two or more atoms of the same element, or two or more different types of atoms. A molecular compound is a chemical compound whose simplest units are molecules.

8. Covalent Bondingand Molecular Compounds H2O A chemical formula indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts. A molecular formula shows the types and numbers of atoms combined in a single molecule of a molecular compound. A diatomic molecule is a molecule containing only two atoms. NaCl CO2 O2

9. Formation of a Covalent Bond As atoms approach each other, their charged particles begin to interact. Nuclei and clouds attract each other - potential energy decreases. • The two nuclei and the two e- clouds repel each other – potential energy increases. • At a given distance, the repulsion equals the attraction, energy potential is at its lowest, and the bond forms.

10. Characteristics of a Covalent Bond Bond length is the distance between two bonded atoms at their minimum potential energy, that is, the average distance between two bonded atoms. Example) The bond length of H-H is 75 pm. At this length, the one electron of each atom is shared by both atoms.

11. Characteristics of a Covalent Bond Bond energy is the energy required to break a chemical bond and form neutral, isolated atoms. Example) The bond energy to break H2 is 436 kJ. Sharing electrons allows each atom to experience the effect of the stable electron configuration of a Noble Gas. Keep in mind that bond lengths and bond energies vary with the types of atoms that have bonded.

12. Bond Length and Bond Energy

13. Multiple Covalent Bonds A covalent bond produced by the sharing of two pairs of electrons between two atoms is called a double bond.

14. Multiple Covalent Bonds A covalent bond produced by the sharing of three pairs of electrons between two atoms is called a triple bond.

15. Multiple Covalent Bonds Double and triple bonds are referred to as multiple bonds.

16. Multiple Covalent Bonds Sample Problem Draw the Lewis structure of methanal (formaldehyde) CH2O

17. Worksheet Covalent Bonding