Electronic Structure Flashcards
(124 cards)
1
Q
What is the number given to each shell called?
A
Principal quantum number
2
Q
What can be said about the energy and principal quantum number when a shell gets further away from the nucleus?
A
The higher it’s energy and the larger it’s principal quantum number is
3
Q
What are shells divided into?
A
Sub-shells
4
Q
What are the 4 types of sub-shell?
A
S
P
D
F
5
Q
What is an orbital?
A
A region of a sub-shell that contains a maximum of 2 electrons with opposite spins
6
Q
What is spin?
A
A type of momentum possessed by an electron which can either be up or down
7
Q
How many electrons can s sub-shells hold?
A
2
8
Q
How many electrons can p sub-shells hold?
A
6
9
Q
How many electrons can d sub-shells hold?
A
10
10
Q
How many electrons can f sub-shells hold?
A
14
11
Q
What can be said about the energy of orbitals in the same sub-shell?
A
They have the same energy
12
Q
What is spin-pairing?
A
When there are 2 electrons in an orbital which spin in opposite directions
13
Q
What shape are s-orbitals?
A
Spherical
14
Q
What shape are p-orbitals?
A
Dumbbell shape
15
Q
What is the formula for the number of electrons a shell can hold?
A
2n^2 (n being shell number)
16
Q
What is electron configuration?
A
The number of electrons and how they’re arranged
17
Q
Why do 4s sub-shells fill first before 3d sub-shells?
A
4s sub-shells have a lower energy level
18
Q
What did Werner Heisenberg came up with?
A
The theory that you cannot know the speed of an electron or it’s exact position
19
Q
What was Heisenberg’s theory called?
A
Uncertainty principle
20
Q
How do ions form?
A
When atoms lose or gain electrons to become positively or negatively charged
21
Q
What is electrostatic attraction?
A
A strong force between positive and negative ions
22
Q
What is an ionic bond?
A
An electrostatic attraction between 2 oppositely charged ions
23
Q
What is an ionic compound?
A
When oppositely charged ions form an ionic bond
24
Q
What are ionic crystals?
A
Giant lattice (regular structure) of ions
25
How does a lattice form?
When each ion is electrostatically attracted in all directions to ions of the opposite charge
26
Describe the electrical conductivity of ionic compounds
Conduct electricity when molten or dissolved, but not when solid
27
Why do ionic compounds not conduct electricity when solid?
There are no mobile ions as they're fixed in position by strong metallic bonds
28
Why do ionic compounds conduct electricity when molten or dissolved?
They have ions that are free to move (mobile ions) so can carry charge
29
Describe the melting and boiling points of ionic compounds?
Have high melting and boiling points
30
Why do ionic compounds have high melting and boiling points?
The giant ionic lattices are held together by strong electrostatic forces (which takes lots of energy to overcome)
31
Describe the solubility of ionic compounds
Tend to dissolve in water
32
Why do ionic compounds tend to dissolve in water?
Water molecules are polar, so the water molecules pull the ions away from the lattice and cause it to dissolve
33
What does polar molecule mean?
Part of the molecule has a negative charge, the other bits have a positive charge
34
How are molecules formed?
When 2 or more atoms bond together
35
What are molecules held together by?
Strong covalent bonds
36
What is a covalent bond?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
37
Give an example of a molecule with triple bonds
Nitrogen (N2)
38
Give an example of a molecule with double bonds
Oxygen (O2)
39
What is different between a single covalent bond and a dative covalent bond?
In a single covalent bond, atoms share electrons with the electrons coming from each atom. Dative covalent bonds shares electrons but both electrons come from the same atom
40
How can you show a dative bond on a diagram?
By an arrow, pointing away from the donor atom
41
What is different about boron trifluoride?
The boron only has 6 electrons on its outer shell
42
What does expanding the octet mean?
Having an outer shell with more than 8 electrons
43
Give an example of a molecule that expands the octet
Sulfur Hexafluoride, has 12 electrons in it's outer shell
44
What does enthalpy mean?
Another word for energy
45
What does the average bond enthalpy tell you?
The strength of a covalent bond
46
What does average bond enthalpy measure?
The average energy needed to break a bond
47
What does the shape of a molecule depend on?
The number of pairs of electrons in the outer shell of the central atom
48
What are shared electrons called?
Bonding pairs
49
What are unshared electrons called?
Lone pairs
50
What do pairs of electrons do?
Repel each other (as they're both negatively charged)
51
Which repels more, lone pairs or bonding pairs?
Lone pairs
52
Why do lone pairs repel more?
Being closer to the central atom causes lone-pairs to take up more of the available 'bonding space'
53
What is electron pair repulsion theory?
That the greatest bond angles are between lone pairs of electrons, and bond angles between bonding pairs are reduced because they're pushed together by lone pair repulsion
54
When drawing shapes of molecules, what does a broken line (e.g. |||||) show?
A bond pointing away from you
55
When drawing shapes of molecules, what does a wedge line show?
A bond pointing towards you
56
When drawing shapes of molecules, what does a line show?
A bond that isn't pointing towards or away from you
57
What is the bond angle of a linear shape?
180°
58
What electron pairs does a linear shape have?
2 bonding pairs, 0 lone pairs
59
Why do linear molecules have a bond angle of 180°?
The pairs of bonding electrons repel each other, so are positioned as far away as possible from each other
60
What electron pairs does a trigonal planar have?
3 bonding pairs, 0 lone pairs
61
What is the bond angle of a trigonal planar?
120°
62
What electron pairs does a non-linear molecule (with 3 electron pairs) have?
2 bonding pairs, 1 lone pair
63
What is the bond angle of a non-linear with 3 electron pairs?
A bit less than 120°
64
What electron pairs does a tetrahedral have?
4 bonding pairs, 0 lone pairs
65
What is the bond angle of a tetrahedral?
109.5°
66
What electron pairs does a trigonal pyramidal have?
3 bonding pairs, 1 lone pair
67
What is the bond angle of a trigonal pyramidal?
107°
68
What electron pairs does a non-linear (with 4 electron pairs) have?
2 bonding pairs, 2 lone pairs
69
What is the bond angle of a non-linear with 4 electron pairs?
104.5
70
What is a molecule with 5 bonding pairs called?
Trigonal bipyramidal
71
What are the bond angles in a trigonal bipyramidal?
90° and 120°
72
Why do trigonal bipyramidal molecules have 2 bond angles?
Because 3 of the atoms will form a trigonal planar shape (120°) and the other 2 atoms will be at 90°
73
What is a molecule with 6 bonding pairs called?
Octahedral
74
What are all the bond angles in an octahedral?
90°
75
What types of bonds can only be purely covalent?
Only bonds between atoms of a single element (e.g. diatonic gases)
76
What is electronegativity?
The ability of an atom to attract the bonding electrons in a covalent bond
77
What is the general trend in electronegativity?
Increases as you move towards Fluorine
78
What is the trend of electronegativity down a group?
It decreases
79
What is the trend of electronegativity across a period?
It increases
80
What does a higher electronegativity number mean?
Means that element is better able to attract the bonding electrons
81
What are the covalent bonds in diatonic gases?
Non-polar
82
What does non-polar mean?
Where the atoms have equal electronegativities and so the electrons are equally attracted to both nuclei
83
What is a polar bond?
A covalent bond where a difference in electronegativity has caused a shift in electron density in the bond
84
In a covalent bond between 2 atoms with different electronegativities, where are the bonding electrons pulled to?
The most electronegative atom
85
In a polar bond, what does the difference in electronegativity between the atoms cause?
A permanent dipole
86
What is a dipole?
A difference in charge between the 2 atoms caused by a shift in electron density in the bond
87
Between 2 atoms, the greater the difference in electronegativity...
… The more polar the bond
88
What do polar molecules have?
An overall dipole
89
What determines whether a polar molecule has an overall dipole?
The arrangement of polar bonds
90
Why does CO2 have no overall dipole?
Because it is a linear molecule, the shape of the molecule is symmetrical. This causes the dipoles to cancel each other out, so it will be non-polar and have no overall dipole
91
For a greater difference in electronegativity, what will the difference in type of bond be?
The less covalent and the more ionic it will be
92
In general, what will the bonds be if the difference in electronegativity is less than 0.4?
Non-polar covalent bonds
93
In general, what will the bonds be if the difference in electronegativity is between 0.4 and 2.0?
Polar covalent bonds
94
In general, what will the bonds be if the difference in electronegativity is greater than 2.0?
Ionic
95
What are intermolecular forces?
Forces between molecules
96
How strong are intermolecular forces compared to covalent, ionic or metallic bonds?
Much weaker
97
What are the 3 types of intermolecular bonding?
Permanent dipole-dipole interactions
Induced dipole-dipole interactions
Hydrogen bonding
98
Which is the strongest of the 3 types of intermolecular bonding?
Hydrogen bonding
99
What does induced dipole-dipole interactions cause?
All atoms and molecules to be attracted to each other
100
What cause a temporary dipole?
When the electrons in an atom are to more side than the other (increasing the charge on that side)
101
What does a temporary dipole cause?
Another temporary induced dipole in the opposite direction of a neighbouring atom (which causes them to attract)
102
What trend in strength of induced dipole-dipole interactions occurs the larger the molecule?
Larger the molecule, the larger the electron clouds meaning stronger induced dipole-dipole interactions
103
Why do molecules with a greater surface area have stronger induced dipole-dipole interactions?
The have more of the electron cloud exposed
104
What can induced dipole-dipole interactions also be called?
London forces
105
What are permanent dipole-dipole interactions?
Where the ẟ+ and the ẟ- charges on polar molecules cause weak electrostatic forces of attraction between molecules
106
What is Hydrogen bonding?
A bond that only occurs when Hydrogen is covalently bonded to fluorine, nitrogen or oxygen
107
What is charge density?
A measure of how much positive or negative charge there are in a certain volume
108
What is the charge density of Hydrogen like?
Very high as it is small
109
What do molecules with Hydrogen bonding normally contain?
-OH or -NH groups
110
What are the properties of molecules with Hydrogen bonding?
Soluble in water
| High melting and boiling points
111
Why do water and ammonia have very high melting points compared to the other hydrides in their group?
Because more energy is needed to break the Hydrogen bonds
112
Why do icebergs float on water?
Ice is less dense than water
113
How are water molecules in ice held together?
By Hydrogen bonds
114
Why is ice less dense than water?
Ice has Hydrogen bonds. Since Hydrogen bonds are long, the molecules in ice will be further apart than in liquid (making it less dense)
115
When drawing Hydrogen bonds, where does the ẟ+ go?
Goes on the H atom
116
When drawing Hydrogen bonds, where does the ẟ- go?
On the electronegative atom
117
What are the bonds and forces like in simple covalent compounds?
Strong bonds within compounds, but weak forces between the molecules
118
What is the electrical conductivity of simple covalent compounds?
They don't conduct electricity (as they're overall uncharged)
119
What is the melting and boiling points of simple covalent compounds like?
Melting and boiling points are low, as the intermolecular forces that hold together the molecules are weak, so don't need much energy to break
120
When melting or boiling and simple covalent compounds, what bonds/forces do you have to break?
Have to break the intermolecular forces that hold together the molecules in a compound (But not the covalent bonds that hold the atoms together in a molecule)
121
What is the trend in melting and boiling points as intermolecular forces get stronger?
Melting and boiling points increase
122
What is the solubility of simple covalent compounds with Hydrogen bonds?
Compounds with Hydrogen bonds can form Hydrogen bonds with water molecules, so will be soluble
123
What is the solubility of simple covalent compounds that are non-polar?
Insoluble
124
What are the 2 factors, as you go down the Group 7 Hydrides, that affect the strength of the intermolecular forces?
The polarity of the molecules decrease, so the strength of the permanent dipole-dipole interactions decreases
The number of electrons in the molecule increases, so the strength of the permanent dipole-dipole interactions increase
