Atoms strive for 8 valence, so they bond Bellwork 1. What is the octet rule? How do atoms reach it? 2. Which elements are exceptions to the octet rule? Atoms strive for 8 valence, so they bond H, He
3. Remind me… What is an ionic bond? A nonmetal takes electron(s) from an atom of a metal
23. Not all atoms gain or lose electrons. Sometimes they share 23. Not all atoms gain or lose electrons. Sometimes they share. This is called a covalent bond. Ionic Covalent
24. A covalent bond occurs when two or more nonmetals share electrons to have a full outer shell.
25. Which of the following are ionic and which are covalent? Metal and nonmetal - ionic CaCl2 CH4 H2O NaF Nonmetal and nonmetal - covalent Nonmetal and nonmetal - covalent Metal and nonmetal - ionic
Covalent Bonds Covalent compounds have different properties from ionic compounds. They are often _________________ ______________ of varying colors, and they have very low __________________. They don’t usually ____________________ electricity well and do not typically ________________________ in water. brittle solids Melting points conduct dissolve
Calculate electrons here 8. Let’s try drawing a Lewis structure for a covalent bond. Use the chart and fill in the steps. Show the Lewis structure for PCl3 below. Electron check! Draw here Calculate electrons here
Writing Lewis Structures total Find the ________ of valence electrons of all atoms in the molecule. Use the ________________ to determine the number of valence electrons Periodic table
Writing Lewis Structures PCl3 5 + 3(7) = 26
Writing Lewis Structures least The central atom is the ___________ abundant element that isn’t _____________. Connect the outer atoms to it by __________ bonds, using a straight line. Each line represents the two electrons that are shared. hydrogen single
Writing Lewis Structures Keep track of the electrons: 26 6 = 20
Writing Lewis Structures outer Fill the octets of the _______ atoms.
Keep track of the electrons: 26 6 = 20 18 = 2
Writing Lewis Structures central Fill the octet of the _______ atom.
Keep track of the electrons: 26 6 = 20 18 = 2 2 = 0
Writing Lewis Structures If you run out of electrons before the central atom has an octet, form ___________ bonds (double or triple bonds only) until it does. multiple
9. Some atoms bond with a double bond. Let’s try one! CO2 Carbon Dioxide ____________ Show the double covalent bonds in CO2 below. Electron check!
10. These are the steps for naming binary covalent compounds: A. The nonmetal farthest on the left of the table is written first. (Except H) Add prefixes to indicate number of atoms. Never write the prefix “mono-” for the first element. Change the ending to –ide for second element.
Molecular Nomenclature Prefixes mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER 1 2 3 4 5 6 7 8 9 10
B. Mononitrogen trioxygen C. MonoNitrogen trioxygen A. Nitrogen + oxygen B. Mononitrogen trioxygen C. MonoNitrogen trioxygen D. Nitrogen trioxide (notice for oxygen, you drop the “y” and change to “i”!)
9. Try these on your own! CCl4 N2O SF6 carbon tetrachloride dinitrogen monoxide sulfur hexafluoride