Bonding what exactly is a bond depends ionic or covalent polar
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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

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Bonding What exactly is a bond? Depends…Ionic or Covalent ? Polar?

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Bonding what exactly is a bond depends ionic or covalent polar

Bonding What exactly is a bond? Depends…Ionic or Covalent? Polar?

NON-POLAR COVALENT=> equal sharingof 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


Molecular polarity

Molecular Polarity

  • Tutorial 1: p. 226

  • Figure 6: p. 228

  • p. 227 #1,2

  • HW: p. 229 #1-7ab

No molecular dipole

=> non-polar molecule

Molecular Dipole is present

=> polar molecule

No molecular dipole

=> non-polar molecule

Molecular Dipole is present

=> polar molecule


Which process requires more energy why

Which process requires more energy?Why?

H2O(l) H2O(g)

or

2 H2O(l) 2 H2(g) + O2(g)


Bonding what exactly is a bond depends ionic or covalent polar

Intermolecular Forces

  • London force (dispersion)

  • due to electrostatic attraction b/w protons in one molecule and electrons of neighbouring molecules

  • strength α # of e-

Cl2bp = -35°C

I2bp = 84°C

Explain the trend in bp.

Cl2 has 34 e-. I2 has 106 e-.

I2 has more e- => greater LDF => higher bp


Bonding what exactly is a bond depends ionic or covalent polar

Intermolecular Forces

  • dipole-dipole force

  • due to attraction of one dipole by surrounding dipoles

  • strength α molecular polarity

CH2O is a polar molecule => has a dipole force, LDF (16 e-)

C2H6 is a non-polar molecule => no dipole force, only LDF (18 e-)

CH2O has higher bp due to dipole-dipole force

CH2Obp = -21°C

C2H6bp = -89°C

Explain the trend in bp.

Include diagrams to support

your explanation.


Bonding what exactly is a bond depends ionic or covalent polar

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.)


Bonding what exactly is a bond depends ionic or covalent polar

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

H2Tebp = -10°C

H2Sebp = -50°C

H2Sbp = -80°C

H2Obp = 100°C

Explain the trend in bp.


Intermolecular forces

Identify the type of IMF

Strongest?

Intermolecular Forces


Properties of liquids

Properties of Liquids

Cohesiveforces:

  • attractions b/w like molecules

    Adhesive forces:

  • attractions b/w unlike molecules


Capillary action

Capillary Action

  • Water is transported in thin tubes from roots to shoots.

  • adhesive forces (b/w H2O and sides of tubes) and cohesive forces (b/w H2O molecules)

  • Water is pulled up against gravity!


Intermolecular forces and properties

Intermolecular Forces and Properties

  • Boiling and melting pt

  • Surface tension

  • Meniscus shape

  • Capillary action

  • Volatility

  • Viscosity

  • Solubility

  • Wetting Action

  • Hydrophobicity


Why is glycerol more viscous than water

Why is glycerol more viscous than water?


Homework

Homework

  • Section 4.7

  • p. 244 #1,2

  • p. 247 #1-6


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