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Alia - Chemistry > Lecture 10-Chemical Bonding IV > Flashcards

Lecture 10-Chemical Bonding IV Flashcards

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1
Q

In an ionic bond, what do the +ve and -ve ions form from?

A 
\+ve = metals
-ve = non-metals
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2
Q

What is an ionic bond?

A

An electrostatic force between cations + anions

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3
Q

What is a covalent bond?

A

An electrostatic force between 2 nuclei + the shared e- pair

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4
Q

What is a dative covalent bond?

A

An electrostatic force between 2 nuclei + the shared e- pair

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5
Q

How strong is a dative covalent bond?

A

It’s indistinguishable from normal covalent once formed

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6
Q

Describe the polarity of the bonds?

A

Ionic = polar
Covalent = both
Dative covalent = often polar

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7
Q

Describe the solubility if the bonds in water?

A

Ionic = soluble
Covalent = depends on the molecule
Dative covalent = Depends on the molecule (often reacts with water)

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8
Q

Describe metallic bonding?

A

Electrostatic attraction between metal ions + mobile delocalised e-

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9
Q

What are delocalised e-?

A

E- not associated with a particular atom

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10
Q

What requirements are needed for metallic bonding?

A

The metal = low ionisation energies
(metal readily gives up their e- —> positive metal ions)
The metal = vacant valence orbitals
(e- move freely between overlapping orbitals)

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11
Q

What does the great strength of metals depend on?

A
  • N.O of e-

- Packing of cations

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12
Q

Why are metals malleable + ductile?

A

+ve ions move over each other because of the e- between

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13
Q

Give 2 characteristics of metals?

A
  • Good conductors of heat + electricity in solid,liquid state
  • Lustrous
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14
Q

What type of forces determine melting + boiling points?

A

Intermolecular forces

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15
Q

Give an example of intramolecular forces?

A
  • Polar covalent

- Non-polar

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16
Q

Give examples of intermolecular forces?

A

Dipole-dipole

Hydrogen bonds

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17
Q

When and where do attractive + repulsive operate?

A

Between e- + protons

when atoms / molecules approach each other

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18
Q

Can attraction be between permanent charges (ions) , permanent dipoles or induced dipoles?

A

Yes

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19
Q

List the intermolecular forces from strongest to weakest

A

Ion-dipole
H bonds
Dipole-dipole
Dispersion forces

20
Q

What is the only non-polar intermolecular force?

A

Dispersion forces

21
Q

How do london dispersion forces form?

A

1) e- = constantly moving in their orbitals
2) at any given moment = more e- on one side of the atom / molecule —> instantaneous temporary dipole
3) this dipole induces anther in a neighbouring molecule
4) Attraction between these dipoles = a weak intermolecular force

22
Q

Where do london dispersion forces occur?

A

Between all types of molecules

23
Q

What does the strength of london dispersion forces depend on?

A

Strength increases with the n.o of e-

24
Q

Describe the significance of london dispersion molecules in boiling points?

A

Noble gases
Halogens
Alkanes

25
Q

Describe the significance of london dispersion molecules in solids?

A

Hardness

26
Q

Describe the significance of london dispersion molecules in behaviour of gases?

A

At low temperatures

27
Q

Describe the significance of london dispersion molecules in cell membrane?

A

Stabilizing lipid bilayers

28
Q

Describe the significance of london dispersion molecules in PROTEINS?

A

Protein structure + self-recognition

29
Q

What are the requirements for permanent molecular dipole-dipole?

A
  • Electronegative difference

- A non-uniform charge distribution in 3-D

30
Q

What is a dipole-dipole bond?

A

Electrostatic attraction between permanent dipoles

31
Q

What do dipole-dipole interactions result in?

A

Higher than expected boiling pints vs mass of the molecule

32
Q

Describe the significance of dipole-dipole reactions?

A

Carbonyls

Protein folding

33
Q

What are ion-dipole forces?

A

Electrostatic interaction between an ion and a uncharged polar molecule

34
Q

What does the strength of ion-dipoles depend on?

A

The charge of the ion + magnitude of the dipole

35
Q

Where are ion-dipoles most common + example?

A

In solution

e.g. KCL dissolving in H20

36
Q

Requirements for H bonding?

A

O- , N- , F-
(small size , high charge density ,lone pair in small orbital)
A H+ atom (donor) in a POLAR BOND

37
Q

What are the properties of H bonds?

A

Weak + easily broken
Directional
Additive

38
Q

Give an example of a positional isomer with H bonds?

A

o-nitrophenol Mp = 43-45

p-nitrophenol Mp = 110-115

39
Q

Name the hydrides?

A

H20
HF
NH3
CH4

40
Q

Why does water form an extensive network of H bonds?

A

O = 2 lone pairs

H2O molecules = 2H atoms

41
Q

Compare the structure of ice to H2O normal structure?

A

Each H2O = H bonded to 4 others in a tetrahedral formation

Ice = diamond-like crystal structure

42
Q

What does water do due to optimal H bonding?

A

Molecules are further apart in liquid water

43
Q

Does ice have a fixed arrangement of H bonds?

A

Yeah

44
Q

What allows the correct pairing of DNA bases?

A

Matching number of H bond donors + acceptors

45
Q

In an alpha helix + beta sheet structure what are the strongest interactions?

A

Between amide N-H and C=O

46
Q

Describe the bonding in cellulose?

A

Multiple H bonds within and between sugar chains (held rigidly)
-Flat sheets of H bonded chains held together by london dispersion

47
Q

What is the strongest intermolecular forces between acetone (ketone with carbonyl) + H2O?

A

Dipole-dipole

Alia - Chemistry (12 decks)

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