1. Part 1: Covalent Bonds And Molecules

2. Objectives Explain what a covalent bond is and what type of elements form them Describe how molecules with covalent bonds are named 2

3. Octet Rule Atoms want to achieve a noble gas electron configuration –s2p6–s2p6 –8 valence electrons in dot structure Exception is hydrogen  wants to have two valence electrons to be like helium (“duet rule”)

4. Ionic Compounds Ex.) NaCl Na achieves octet rule by losing 1 electron and Cl achieves octet rule by gaining 1 electron Valence electrons get transferred from metal to nonmetal Ionic compounds contain ions (cation + anion) held together by ionic bonds

6. Some nonmetals are unlikely to lose or gain electrons Ex. Nonmetal elements in Group 4 have four electrons in their outer levels To gain or lose four electrons is highly unlikely due to their protons’ attraction Covalent Bonds

7. Molecular Compounds Ex.) H 2 O No ions!!! All atoms are held together by covalent bonds Electrons get shared so the octet rule can be met for all atoms Two non-metals

8. The stable attraction that forms between nonmetal atoms when they share electrons is known as a covalent bond The neutral particle that forms due to electron sharing is called a molecule Use Lewis Dot structures for clarity Covalent Bonds A water molecule

9. A single covalent bond is made up of two shared electrons A water molecule contains two single bonds in which each atom contributes one electron to the other in the bond The result: a stable outer energy level for each atom in the molecule: 2 for H and 8 for O Covalent Bonds

10. Molecule Example (water) Molecule- Smallest part of molecular compound held together by covalent bonds

11. A covalent bond also can contain more than one pair of electrons An example of this is the bond in oxygen (O 2 ) or nitrogen (N 2 ) Covalent Bonds

12. Molecular Formula Structural Formula Molecule Representation H2OH2O

13. Naming Molecular (Covalent) Compounds No molecular compounds will ever contain metals or contain ions You need to forget about charges when naming molecular compounds

14. Rules for Naming Molecular Compounds 1.Use full name of first element 2.Second element uses the “root” name of the element + the “ide” suffix. 3.Use hydrate prefixes to denote how many atoms of each are in the compound. Ex.) CO 2 = Carbon dioxide 4.Prefix “mono” is never used in front of the 1 st element and the 2 nd element only uses the prefix “mono” if it is oxygen. Ex.) carbon monoxide

15. Examples of Naming Molecules… OF 2 CO NH 3 P 2 I 5 H 2 O Oxygen difluoride Carbon monoxide NOT monooxide Nitrogen trihydride Diphosphorus pentiodide (drop “a” from penta) Dihydrogen monoxide NONE OF THESE COMPOUNDS CONTAIN METALS!!! HYDROGEN = NOT A METAL!!!

16. Objectives Explain what a covalent bond is and what type of elements form them Describe how molecules with covalent bonds are named 16