L10: Metallic & Intermolecular Bonding Flashcards
Describe the interactions in metallic bonding
Electrostatic attraction between metal ions and mobile, delocalised electrons
What are delocalised electrons?
They are not associated with a particular atom
What are the prerequisites for metallic bonding to occur?
1) The metal should have low ionisation energies (able to give up their electrons to form positive metal ions)
2) The metal should have vacant valence orbitals to allow free movement of electrons
Fill in the gap:
Metallically bonded compounds are __(1)__ conductors of heat and electricity in in solid and __(2)__ state
(1) good
(2) liquid
Comment on the lustre of metallic compounds
Metallic compounds have a high lustre
True or false: Metallic compounds are relatively malleable and ductile
True
What are intramolecular forces?
Bonds holding atoms together within a molecule
What are intermolecular forces?
Attractive forces between molecules
Which is stronger, intermolecular or intramolecular forces?
Intramolecular
What are the four types of intermolecular forces? List in order of strength (strongest first)
1) Ion-dipole
2) Hydrogen bonds
3) Dipole-dipole
4) Dispersion
Which bonds form between polar molecules?
Ion-dipole, hydrogen, and dipole-dipole
Which bonds form between non-polar molecules?
Dispersion (van der Waals/London)
True or false: London dispersion forces are formed between temporary dipoles. These dipoles come about because of the uneven distribution of electrons in their orbitals
True
True or false: London dispersion forces form between temporary dipoles
True
True or false: Dipole-dipole interactions form between temporary dipoles
False. They relate to permanent dipoles
True or false: Dipole-dipole interactions act in addition to Van der Waals
True
How do dipole-dipole interactions effect boiling point?
Result in higher BP than expected from the mass of the molecule
In which two areas are dipole-dipole interactions significant?
1) Carbonyls
2) Protein folding
Fill in the gaps:
__(1)__-dipole forces are electrostatic interactions between an __(2)__ and an __(3)__ __(4)__ molecule
(1) ion
(2) ion
(3) uncharged
(4) polar
What factor effects the strength of an ion-dipole bond?
Strength depends on the charge on the ion and the magnitude of the dipole
Where are ion-dipole forces most common?
In solution.
E.g. NaCl dissolving in water
What are the two requirements for a hydrogen bond?
1) An electronegative atom (O, N, or F) to act as the acceptor
2) A hydrogen atom in a polar bond (N-H, O-H, or F-H) to act as the donor
True or false: Hydrogen bonds are stronger than other dipole-dipole interactions
True
True or false: Hydrogen bonds are non-directional
False. Hydrogen bonds are directional
True or false: Although they are relatively strong for intermolecular forces, hydrogen bonds are weak and easily broken compared to covalent bonds
True
Give six areas in which hydrogen bonding plays a significant role
1) Physical state of water
2) Stabilise macromolecules
3) DNA double helix, base pairing
4) Protein secondary structure; alpha helices, beta sheets
5) Enzyme-substrate and antibody-antigen interactions
6) Solubility of compounds in water
Why does water form such an extensive network of hydrogen bonds?
Each oxygen atom has two lone pairs and each molecule has two hydrogen atoms
True or false: The base pairs match each other based on the number of hydrogen bonds each can donate/accept
True
True or false: In alpha helices and beta sheets, hydrogen bonds form between amine (N-H) and C=O
True
In addition to hydrogen bonds, what links can be formed by covalent and ionic bonding in secondary protein structures?
Covalent disulphide links (R-S-S-R)
Ionic salt bridges (—CO2—-NH3—-
Which intermolecular bonds hold sugar chains together in cellulose to form flat sheets?
Hydrogen bonds
Which intermolecular bonds hold flat sheets of hydrogen-bonded sugar chains together in cellulose?
Van der Waals
