Presentation on theme: "Bonding What exactly is a bond? Depends…Ionic or Covalent? Polar? NON-POLAR COVALENT=> equal sharing of electron pair 0 < ∆EN < 0.4 POLAR COVALENT= unequal."— Presentation transcript:
Bonding What exactly is a bond? Depends…Ionic or Covalent? Polar? NON-POLAR COVALENT=> equal sharing of electron pair 0 < ∆EN < 0.4 POLAR COVALENT= unequal sharing of electron pairs, e-’s spend more time closer to one atom, 0.4 < ∆EN < 1.7 IONIC “BOND”= transfer of electrons, no physical connection to one another, atoms are held together by an electrostatic attraction, ∆EN > 1.7
No molecular dipole => non-polar molecule Molecular Polarity Tutorial 1: p. 226 Figure 6: p. 228 p. 227 #1,2 HW: p. 229 #1-7ab Molecular Dipole is present => polar molecule No molecular dipole => non-polar molecule Molecular Dipole is present => polar molecule
Which process requires more energy? Why? H 2 O (l) H 2 O (g) or 2 H 2 O (l) 2 H 2(g) + O 2(g)
Intermolecular Forces London force (dispersion) due to electrostatic attraction b/w protons in one molecule and electrons of neighbouring molecules strength α # of e - Cl 2 bp = -35°C I 2 bp = 84°C Explain the trend in bp. Cl 2 has 34 e -. I 2 has 106 e -. I 2 has more e - => greater LDF => higher bp
Intermolecular Forces dipole-dipole force due to attraction of one dipole by surrounding dipoles strength α molecular polarity CH 2 Obp = -21°C C 2 H 6 bp = -89°C Explain the trend in bp. Include diagrams to support your explanation. CH 2 O is a polar molecule => has a dipole force, LDF (16 e - ) C 2 H 6 is a non-polar molecule => no dipole force, only LDF (18 e - ) CH 2 O has higher bp due to dipole-dipole force
Predict which substance has the stronger dipole force: HCl or HBr HCl is the more polar molecule (ΔEN is greater) => stronger dipole forces (Draw diagrams to support your explanation.)
Intermolecular Forces Hydrogen bonding due to attraction of a H bonded to a highly EN atom (O, N or F) in one molecule by the lone pair of e - on a highly electronegative atom of a neighbouring molecule H 2 Tebp = -10°C H 2 Sebp = -50°C H 2 Sbp = -80°C H 2 Obp = 100°C Explain the trend in bp.
Intermolecular Forces Identify the type of IMF Strongest? Identify the type of IMF Strongest?
Properties of Liquids Cohesive forces: attractions b/w like molecules Adhesive forces: attractions b/w unlike molecules
Capillary Action Water is transported in thin tubes from roots to shoots. adhesive forces (b/w H 2 O and sides of tubes) and cohesive forces (b/w H 2 O molecules) Water is pulled up against gravity!