Forces of Attraction Objectives: 1. State the kinetic theory of matter. 2. Describe and compare types of intramolecular and intermolecular forces.

Vocabulary Building/Review What is the difference between intra- and inter-? What are 3 types of forces (aka, bonds) that hold particles (or atoms) together? Think “intramural sports” and “interstates”. “within”; “between”

Intramolecular Forces Def.: attractive forces that hold particles (atoms) together in ionic, covalent, and metallic bonds 3 types: (examples of each?) Ionic – between _______ and _________. Covalent: b/t (+) nuclei and (-) electrons Metallic: b/t metal cations(?) and mobile(?) electrons Cations; anions + charged ions; moving from atom to atom

Intermolecular Forces Hold molecules(?) together 3 types: Dispersion/London forces Dipole-dipole forces Hydrogen bonds

1. Dispersion/London Forces Weak forces between “identical nonpolar molecules” (diatomic molecules) Examples? Results from the shifting of electrons in the electron clouds What are the states of matter of the halogens? Explain why……. More valence electrons as you move down the halogens means a stronger intermolecular force, so molecules are pulled closer together.

2. Dipole-dipole Forces Between polar molecules: molecules formed from different elements Some elements are more electronegative than others, and will be the “(-) end” of the molecule, while the other end is more (+). Slightly stronger than dispersion forces, but still pretty weak. Example: HCl (Which atom would have the negative charge?) What is the most electronegative element? F Chlorine

3. Hydrogen Bonds A dipole-dipole attraction between hydrogen and “a small, highly electronegative atom with at least one lone electron pair” (F, O, or N) Example??? water

Review and Apply What types of intermolecular forces must be overcome to: melt ice? boil water? melt NaCl? sublime I2? Mass/volume

Review and Apply, continued…. Which of the following compounds can form dipole-dipole forces? Cl2 c. NO CO d. CH4 Which of the following molecules can form hydrogen bonds? Which would have only dispersion forces? H2 c. NH3 HCl d. HF 2. B and C 3. B and D; A