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physical chemistry a level > bonding > Flashcards

bonding Flashcards

1
Q

What is ionic bonding ?

A
  • the electrostatic force of attraction between oppositely charged ions formed by electron transfer
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2
Q

What is the structure of ionic crystals ?

A
  • giant ionic lattices
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3
Q

What is giant ionic lattice ?

A
  • a structure with a regular, repeating pattern of alternating positive and negative ions
  • the oppositely charged ions are held together by strong electrostatic force of attraction
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4
Q

Why is ionic bonding stronger and the melting point higher when the ions are smaller and have higher charges

A
  • the smaller an ion, the more tightly packed they can be in a lattice = a shorter distance = a stronger electrostatic force
  • bigger charge = bigger electrostatic force
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5
Q

Why is a magnesium ion smaller than a sodium ion ?

A
  • magnesium has a greater nucleic charge
  • so more attraction between protons and outer shell electrons
  • so a smaller atomic radius
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6
Q

Why are positive ions smaller than their atoms ?

A
  • as an ion, there is now one less shell of electrons
  • so ration of protons to electrons has increased
  • so there is a greater net force on the remaining electrons
  • so they are held together more closely
  • so a smaller radius
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7
Q

Why are negative ions larger than their atoms ?

A
  • the negative ion has more electrons but the same number of protons
  • so the attraction from the nucleus is more shared over electron
  • so attraction per electrons is less and the electrons aren’t pulled as close together
  • so the radius is bigger
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8
Q

What is the trend of ionic radii when you go down the group ?

A
  • the ionic radii increases
  • because the ions going down the group have more shells of electrons
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9
Q

What is a covalent bond ?

A
  • a covalent bond is a shared pair of electrons
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10
Q

What are properties of simple covalent structures ?

A
  • have a low melting and boiling points
  • because even though there are strong covalent bonds between atoms
  • there are weak intermolecular forces between molecules
  • which do no require a lot of energy to break
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11
Q

What are examples of simple covalent structures ?

A
  • iodine
  • ice
  • carbon dioxide
  • water
  • methane
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12
Q

What are the properties of giant covalent structures ?

A
  • high melting and boiling points
  • because a large amount of energy is needed to break the large number of strong covalent bonds
  • usually cannot conduct electricity because there are no mobile ions or electrons to carry a current
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13
Q

What are examples of giant covalent structures ?

A
  • diamond
  • graphite
  • silicon dioxide
  • silicon
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14
Q

What is metallic bonding ?

A
  • the electrostatic force of attraction between the positive metal ions and a sea of delocalised electrons
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15
Q

What is metallic bonding ?

A
  • the electrostatic force of attraction between the positive metal ions and the delocalised electrons
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16
Q

What are the factors that affect the strength of a metallic bond ?

A
  • number of charge
    • more protons = stronger bond
  • number of delocalised electrons per atom
    • more delocalised electrons = stronger bond
  • size of ion
    • smaller ion = stronger bond
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17
Q

What are the factors that affect the strength of a metallic bond ?

A
  • number of charge
    • more protons = stronger bond
  • number of delocalised electrons per atom
    • more delocalised electrons = stronger bond
  • size of ion
    • smaller ion = stronger bond
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18
Q

Why do metallic structures have high boiling points ?

A
  • there are strong electrostatic forces of attraction between the positive ions and the sea of delocalised electrons
  • which require a lot of energy to break
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19
Q

Why do metallic structures have high boiling points ?

A
  • there are strong electrostatic forces of attraction between the positive ions and the sea of delocalised electrons
  • which require a lot of energy to break
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20
Q

Why do giant ionic lattice have high melting and boiling points ?

A
  • because there are strong electrostatic forces between oppositely charged ions
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21
Q

What are the names of the shapes of molecules ?

A
  • linear
  • non-linear / bent
  • trigonal planar
  • trigonal pyramidal
  • tetrahedral
  • trigonal bipyramidal
  • octahedral
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22
Q

If a molecule has 1 bonding pair and 0 lone pairs, what is the name and bond angle ?

A
  • linear
  • 180º
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23
Q

If a molecule has 2 bonding pairs and 0 lone pairs, what is the name and bond angle ?

A
  • linear
  • 180º
24
Q

If a molecule has 2 bonding pairs and 2 lone pairs, what is the name and the bond angle ?

A
  • non - linear / bent
  • 104.5º
25
Q

If a molecule has 3 bonding pairs and 0 lone pairs, what is the name and the bond angle ?

A
  • trigonal planar
  • 120º
26
Q

If a molecule has 3 bonding pairs and 1 lone pair, what is the name and bond angle ?

A
  • trigonal pyramidal
  • 107º
27
Q

If a molecule has 4 bonding pairs and 0 lone pairs, what is the name and bond angle ?

A
  • tetrahedral
  • 109.5º
28
Q

If a molecule has 5 bonding pairs and 0 lone pairs, what is the name and bond angle ?

A
  • trigonal bipyramidal
  • 120º or 90º
29
Q

If a molecule has 6 bonding pairs and 0 lone pairs, what is the name and bond angle ?

A
  • octahedral
  • 90º
30
Q

If a molecule has 4 bonding pairs and 2 lone pairs, what is its shape and bond angle ?

A
  • square planar
  • 90º
  • is is a variation of the octahedral shape
  • e.g = XeF4
31
Q

If a molecule has 5 bonding pairs and 1 lone pairs, what is the name and shape ?

A
  • square pyramidal
  • 90º
  • a variation of octhahedral
  • e.g = BrF5
32
Q

If a molecule has 2 bonding pairs and 3 lone pairs, what is the name and bond angle ?

A
  • linear
  • 180º
  • e.g = I_3
33
Q

If a molecule has 3 bonding pairs and 2 lone pairs what is the shape and bond angle of ?

A
  • t-shape
  • 90º
34
Q

If a molecule has 4 bonding pairs and 1 lone pair what is the name and bond angle ?

A
  • a variation of trigonal bipyramidal
  • 120º and 90º
35
Q

What is electronegativity ?

A
  • the tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself
36
Q

What factors affect electro negativity ?

A
  • atomic radius
  • shielding
  • nuclear charge
37
Q

How does electro negativity change when you go across a period ?

A
  • electro negativity increases
  • because nuclear charge increases and atomic radius is decreasing ( because electrons in the same shell as being pulled in more )
38
Q

How does electron negativity change as you go down a group ?

A
  • electro negativity decreases
  • because atomic radius increases
  • and shielding increases
39
Q

What are the most electronegative atoms

A
  • fluorine
  • oxygen
  • nitrogen
  • chlorine
40
Q

What do electron pair do in a molecule and how do lone pairs affect this ?

A
  • the bonding pairs of electrons repel to get as far as part as possible
  • if there are no lone pairs the bonding pairs repel each other equally
  • if there are lone pairs, the lone pairs repel more than the bonding pair
  • which causes the bond angle to change
41
Q

What is the electro negativity difference in a covalent molecule ?

A
  • very small ( or the same )
  • as the atoms have similar electronegativity values
42
Q

What will the electronegativity difference be in an ionic molecule ?

A
  • very large difference
  • as one is a positive ion and one is a negative ion
43
Q

What is a permanent dipole ?

A
  • it is a polar covalent bond
  • which happens when the elements in the bond have different electronegativity values
  • and so there is an unequal distribution of electrons
44
Q

What are non-polar molecules ?

A
  • when the molecule is symmetrical ( all the bonds are identical and there are no lone pairs )
  • so the individual dipoles cancel each other out so there is no net dipole
  • meaning the molecule is non-polar
45
Q

What is a polar molecule

A
  • when the molecule is asymmetrical
  • so one side is more negative than the other
  • e.eg CH3Cl
46
Q

What are the three types of intermolecular forces ?

A
  • Van der Wall
  • dipole - dipole
  • hydrogen bonds
47
Q

What are Van der Waal forces ?

A
  • in a molecule, the electrons are moving constantly and randomly
  • so the electrons density at one point can me more on one side than it is on the other side
  • so a small temporary ( or transient ) dipole can form
  • which can cause temporary dipoles to form on the neighbouring molecules ( these are called induced dipoles )
48
Q

Where do Van der Walls forces form ?

A
  • between all molecular forces and noble gases
  • not in ionic substances
49
Q

What factors affect the size of Van der Waal forces ?

A
  • the more electrons in the molecule
  • as it means that temporary dipoles have a higher chance of forming
  • so the Van der Waal forces are greater
50
Q

Why do boiling points increase as we go down group 7

A
  • number of electrons increases as we go down the group
  • so the Van der Waal forces will be greater
  • so more energy is needed to break them
51
Q

How does the shape of a molecule affect Van der Waal forces ?

A
  • longer chain molecules have a larger surface area between molecule for Van der Waal forces to form
  • compared to spherical shaped branched molecules
  • so the overall Van der Waal forces are stronger
52
Q

What are dipole - dipole forces ?

A
  • they occur between polar molecules
  • they are weak electrostatic forces of attraction in between the positive dipole of one molecules and the negative dipole of another molecule
  • they occur in addition to Van der Waal forces
53
Q

What are hydrogen bonds ?

A
  • bonds between an hydrogen atom and a lone pair in the three most electronegative atoms
  • which are fluorine, oxygen and nitrogen
  • occurs in addition to Van der Waal forces
54
Q

What is the strongest type of intermolecular bond

A

Hydrogen bonding

55
Q

Why do H20,NH3 and HF all have anomalously high boiling points ?

A
  • because of the hydrogen bonds between molecules
56
Q

What are the 4 types of crystal structure ?

A
  • giant ionic lattice
  • giant metallic structure
  • simple covalent structure
  • giant covalent (macromolecular)

physical chemistry a level (4 decks)

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