bonding Flashcards
(56 cards)
1
Q
What is ionic bonding ?
A
- the electrostatic force of attraction between oppositely charged ions formed by electron transfer
2
Q
What is the structure of ionic crystals ?
A
- giant ionic lattices
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
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
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
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
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
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
9
Q
What is a covalent bond ?
A
- a covalent bond is a shared pair of electrons
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
11
Q
What are examples of simple covalent structures ?
A
- iodine
- ice
- carbon dioxide
- water
- methane
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
13
Q
What are examples of giant covalent structures ?
A
- diamond
- graphite
- silicon dioxide
- silicon
14
Q
What is metallic bonding ?
A
- the electrostatic force of attraction between the positive metal ions and a sea of delocalised electrons
15
Q
What is metallic bonding ?
A
- the electrostatic force of attraction between the positive metal ions and the delocalised electrons
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
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
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
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
20
Q
Why do giant ionic lattice have high melting and boiling points ?
A
- because there are strong electrostatic forces between oppositely charged ions
21
Q
What are the names of the shapes of molecules ?
A
- linear
- non-linear / bent
- trigonal planar
- trigonal pyramidal
- tetrahedral
- trigonal bipyramidal
- octahedral
22
Q
If a molecule has 1 bonding pair and 0 lone pairs, what is the name and bond angle ?
A
- linear
- 180º
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
If a molecule has 3 bonding pairs and 0 lone pairs, what is the name and the bond angle ?
- trigonal planar
- 120º
26
If a molecule has 3 bonding pairs and 1 lone pair, what is the name and bond angle ?
- trigonal pyramidal
- 107º
27
If a molecule has 4 bonding pairs and 0 lone pairs, what is the name and bond angle ?
- tetrahedral
- 109.5º
28
If a molecule has 5 bonding pairs and 0 lone pairs, what is the name and bond angle ?
- trigonal bipyramidal
- 120º or 90º
29
If a molecule has 6 bonding pairs and 0 lone pairs, what is the name and bond angle ?
- octahedral
- 90º
30
If a molecule has 4 bonding pairs and 2 lone pairs, what is its shape and bond angle ?
- square planar
- 90º
- is is a variation of the octahedral shape
- e.g = XeF4
31
If a molecule has 5 bonding pairs and 1 lone pairs, what is the name and shape ?
- square pyramidal
- 90º
- a variation of octhahedral
- e.g = BrF5
32
If a molecule has 2 bonding pairs and 3 lone pairs, what is the name and bond angle ?
- linear
- 180º
- e.g = I_3
33
If a molecule has 3 bonding pairs and 2 lone pairs what is the shape and bond angle of ?
- t-shape
- 90º or trigonal planer at 120 degrees
34
If a molecule has 4 bonding pairs and 1 lone pair what is the name and bond angle ?
- seesaw = a variation of trigonal bipyramidal
- 120º and 90º
35
What is electronegativity ?
- the tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself
36
What factors affect electro negativity ?
- atomic radius
- shielding
- nuclear charge
37
How does electro negativity change when you go across a period ?
- electro negativity increases
- because nuclear charge increases and atomic radius is decreasing ( because electrons in the same shell as being pulled in more )
38
How does electron negativity change as you go down a group ?
- electro negativity decreases
- because atomic radius increases
- and shielding increases
39
What are the most electronegative atoms
- fluorine
- oxygen
- nitrogen
- chlorine
40
What do electron pair do in a molecule and how do lone pairs affect this ?
- 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
What is the electro negativity difference in a covalent molecule ?
- very small ( or the same )
- as the atoms have similar electronegativity values
42
What will the electronegativity difference be in an ionic molecule ?
- very large difference
- as one is a positive ion and one is a negative ion
43
What is a permanent dipole ?
- 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
What are non-polar molecules ?
- 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
What is a polar molecule
- when the molecule is asymmetrical
- so one side is more negative than the other
- e.eg CH3Cl
46
What are the three types of intermolecular forces ?
- Van der Wall
- dipole - dipole
- hydrogen bonds
47
What are Van der Waal forces ?
- 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
Where do Van der Walls forces form ?
- between all molecular forces and noble gases
- not in ionic substances
49
What factors affect the size of Van der Waal forces ?
- 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
Why do boiling points increase as we go down group 7
- 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
How does the shape of a molecule affect Van der Waal forces ?
- 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
What are dipole - dipole forces ?
- 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
What are hydrogen bonds ?
- 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
What is the strongest type of intermolecular bond
Hydrogen bonding
55
Why do H20,NH3 and HF all have anomalously high boiling points ?
- because of the hydrogen bonds between molecules
56
What are the 4 types of crystal structure ?
- giant ionic lattice
- giant metallic structure
- simple covalent structure
- giant covalent (macromolecular)
