S1-L10: Metallic & Intermolecular Bonding Flashcards
Outline and describe Ionic bonding
- electrostatic attraction between two oppositely charged ions
- strong
- polar bond: A+ -B
- solid at room temp
- water soluble
Briefly explain what Covalent bonding is
- electrostatic force between two nuclei AND shared e- pair
- ->each atom provides equal e-‘s
- strong
- gases/liquids or solids at room temp
- depends on molecule
- can be non-polar/polarised (A-B)
What is Dative covalent bonding and it’s properties?
- one atom provides both e-‘s in shared pair
- ->indistinguishable from normal covalent once formed
- strong
- gases, liquids OR solid at room temp
- dependent on molecule often interact with water
- often polar (A–>B)
Describe metallic bonding (refer to figure 1)
- electrostatic attraction between metal ions AND mobilised e-‘s
- delocalised e-‘s not associated with particular atom
State the requirements for metallic bonding
-metal should have low
What are the key characteristics of metals?
- great strength–>depends on n. of e-‘s AND packing of cations
- good heat & electricity conductor in solid plus liquid state
- malleable AND ductile
- lustrous
Define “Intramolecular Forces” (figure 2)
-hold atoms together within molecule
What are “Intermolecular forces”? (figure 3)
-attractive forces between molecules
How do Intramolecular and Intermolecular forces compare?
-intermolecular forces much weaker than intramolecular forces
Outline the different intermolecular force’s types from strongest to weakest AND which ones are polar AND non-polar molecules
- going strongest to weakest:
- Ion-Dipole forces/H-bonds/ dipole-dipole forces/ Van der Waals forces
- all states are polar molecule except Van der Waals which is non-polar
Describe London Dispersion forces (Van Der Waals/ London forces)
(refer to figure 4)
- e-‘s constantly moving in orbitals
- ->any given moment may be more to one side of atom/molecule than other
- ->causes instantaneous (temporary) dipole
- ->attraction
Briefly explain what Dipole-Dipole interactions are (figure 5)
- relate to permanent molecular dipoles
- ->found in bonds with electronegativity difference
- ->molecular dipoles require non-uniform charge distribution in 3D
- electrostatic attraction between permanent dipoles
What is the effect of dipole-dipole interactions and their significance?
- act in addition to London (VdW) interactions
- results in higher b. points than expected from mass of molecule
- significance: carbonyls/protein folding
State what Ion-Dipole forces are and describe them (refer to figure 6)
- electrostatic interaction between ion AND uncharged polar molecule
- ->strength depends on charge on ion AND dipole’s magnitude
- most common in solution–>like KCl in water
What are the conditions for Hydrogen bonding?
- electronegative atom- O/N or F (delta -)
- ->small size/high charge density/ lone e- pairs in small orbital (acceptor)
- delta + H atom (donor) in polar bond–>usually N-H/ O-H OR F-H
Are there any other possible donors? (refer to figure 7)
- experimental evidence exists to prove other donors in some molecules
- ->depends on bond polarisation
Outline and compare the structure of water and ice (figure 8)
- each water molecule H-bonded to 4 others in tetrahedral formation
- ice has diamond like structure
- Ice: fixed arrangements of H-bonds
- water: disorganised H-bonds break AND reform
Boiling points of hydrides
-figure 9
How is hydrogen bonding involved in DNA? (figure 10)
-matching n. of H bond donors and acceptors allows correct pairing of DNA bases
Outline how hydrogen bonding is involved Alpha helix and beta structures
- alpha helix AND beta sheets structures
- ->strongest interactions between amide N-H and C=O
Why is cellulose important?
- major plant cell wall component
- ->found in wood AND plant fibers/ derivatives used in textiles/ toiletries AND food products
Describe the structure & bonding in cellulose
- polymer of glucose
- sugar chains held rigidly together by multiple H bonds within AND between chains
- flat sheets of H-bonded chains held together by London dispersion (VdW) forces
Outline the solubility of the following substances:
Solute–> Solvent–> IM force–> soluble
1-Sodium Chloride
2-Ehtanol
3-Hexane
1-Sodium Chloride–> water–> Ion-dipole–> Yes
2-Ethnaol–> water–> h-bonding–> Yes
3-Hexane–> water–> N/A–> No
Summary of lecture
- metallic bonding
- intermolecular forces
- -> types of I. Forces: Dispersion/ dipole-dipole/ ion-dipole/ H-bonding
- significance of polarity-induced AND permanent
- significance of different types of intermolecular force AND examples
Exercise: What is the strongest intermolecular force between acetone AND water? :
dipole/ ion-dipole/ H-bonding/ London dispersion
-dipole
