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Chemistry > Bonding > Flashcards

Bonding Flashcards

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1
Q

Explain why metals are malleable

A

planes of metal ions can slide over each other

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2
Q

Electronegativity

A

power of an atom to attract the pair of electrons in a COVALENT bond

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3
Q

Explain hydrogen bonding

A
  • F/N/O are more electronegative than hydrogen
  • dipole formed with partially negative atom and partially positive hydrogen
  • bond formed between H and lone pair on F/N/O on adjacent molecule
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4
Q

Explain why diamond and graphite both have high melting points

A
  • macromolecular

- MANY STRONG covalent bonds need to BROKEN

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5
Q

Explain why graphite is soft

A

weaker van der Waals forces between layers of carbon atoms so can slide over each other

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6
Q

Describe change in motion of ions in NaCl below melting point

A

vibrate faster about a fixed point

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7
Q

Explain why bond angle is equal in a molecule without lone pairs

A

all bonding pairs of electrons repel equally

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8
Q

Suggest why lone pairs of electrons are opposite each other in a molecule

A

lone pairs repel each other more than with bonding pairs so are as far apart as possible

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9
Q

Suggest why lone pairs repel more than bonding pairs

A
  • bonding pairs of electrons are held in a bond further from nucleus of central atom
  • lone pairs are held close to positively charged nucleus
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10
Q

Define permanent dipole

A

unequal sharing of electrons which creates a partially positive and partially negative end

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11
Q

Explain why a molecule can be polar

A
  • lone pairs

- one atom is more electronegative so electron density is attracted towards it

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12
Q

Define polar bond

A
  • bonding pair of electrons is shared unequally

- partial charges at each end of bond

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13
Q

Explain why a molecule has covalent bonding over ionic

A

small difference in electronegativity between atoms so more equal sharing of electrons

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14
Q

Explain why iodine exists as simple molecules where carbon does not

A
  • carbon makes four bonds so it macromolecular

- iodine forms one bond

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15
Q

Explain formation of hydrogen bonding between protein molecules

A

between lone pair on partially negative O in C=O group and partially positive H in N-H group

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16
Q

Explain how metals conduct heat

A
  • delocalised electrons are free to move and carry heat - metal ions are closely packed so kinetic energy is passed between them
17
Q

Electronegativity values of the following:

H, C, N, O, F, Cl, Br

A 
H 2.1 
C 2.5
N 3.0
O 3.5
F 4.0
Cl 3.0
Br 2.8
18
Q

Factors increase van der Waals

A
  • higher molecular mass

- straight chains pack closer than branched chains

19
Q

Compare structure of graphite and diamond

A

Graphite
- three covalent bonds forming hexagonal planes of carbon atoms (bond angle 120)
- weak van der Waals between hexagonal planes
- delocalised electrons
Diamond
- four covalent bonds (bond angle 109.5)

20
Q

State anomalous properties of water and the reason for them

A
  • high boiling point
  • water is denser than ice (forms tetrahedral structure)
  • results from hydrogen bonding
21
Q

Explain which out of HBr and Br2 has the highest melting point

A
  • Br2 since it has a higher Mr

- van der Waals forces are stronger that permanent dipole-dipole forces and van der Waals forces in HBr

22
Q

State bond angle in ethene and explain why

A
  • 120 degrees
  • x3 bonding sites around carbon
  • double bonds almost as strongly as single bonds
23
Q

Propanone contains oxygen and hydrogen atoms. Explain why is does not contain hydrogen bonding.

A
  • hydrogens are all bonded to carbon atoms
  • not a large enough difference in electronegativity values of C and H to create a dipole
  • no H bonding between hydrogen and lone pairs on oxygen
24
Q

Explain why there are induced dipole-dipole forces in alcohol molecules

A
  • random movement of electrons creates instantaneous dipole in C-H bond
  • dipole induces dipole in C-H bond of neighbouring molecule
  • dipoles attract
24
Q

Suggest which factor is most important in determining solubility of a molecule in water and why

A
  • strength of dipole-dipole forces between molecules
  • compared to energy released by hydrogen bond between molecule and water
  • if H bond releases sufficient energy then molecule is soluble in water
    (Do not just mention H bonds are STRONGER)
25
Q

Define ionic, covalent and metallic bond

A
  • ionic = electrostatic attraction between oppositely charged ions in a lattice
  • covalent = shared pair of electrons between atoms
  • metallic = electrostatic attraction between delocalised electrons and positive ions arranged in a lattice
26
Q

Explain why a branched alcohol is more soluble in water compared to a straight chain alcohol

A
  • molecules of alcohol cannot pack close together
  • weaker instantaneous dipole-dipole forces
  • energy from H bonds between alcohol and water is sufficient to overcome attraction between alcohol molecules
    (do not mention more contact points for H bonds or reference surface area)
27
Q

Give other names that refer to van der Waals forces

A
  • induced/ temporary dipole forces
  • dispersion forces
  • London forces
28
Q

Key point to remember when describing bonding/forces

A

must mention between ATOMS or MOLECULES

29
Q

Electron pair repulsion theory

A
  • electron pairs repel as far apart as possible

- lone pairs repel more than bonding pairs

30
Q

Suggest why electron pair repulsion theory cannot be used to predict shape of transition metal complex

A

Too many electrons in d subshell

Chemistry (10 decks)

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