Chemical Bonding Flashcards
1
Q
How do atoms get the same number of electrons as the noble gases
A
Gain, lose or share electrons
2
Q
The octet rule
A
When atoms bond, they lose,share or gain electrons so that they have eight electrons in their outer shell
3
Q
What’s different about elements near the noble gas helium?
A
Do not obey octet rule, seek 2 electrons on outer shell eg.hydrogen or lithium
4
Q
Ammonium ion
A
NH4+
5
Q
Carbonate ion
A
CO3 ^-2
6
Q
Hydrogen carbonate
A
HCO3-
7
Q
Chromate
A
CrO4-
8
Q
Dichromate ion
A
Cr2 O7 -2
9
Q
Cyanide ion
A
CN -
10
Q
Thiosulphate
A
S2 O3 -2
11
Q
Hydroxide ion
A
OH-
12
Q
Manganate
A
MnO4-
13
Q
Nitrate
A
NO3-
14
Q
Nitrite
A
NO2-
15
Q
Phosphate
A
PO4-3
16
Q
Sulphate
A
SO4 -2
17
Q
Sulphite
A
SO3 -2
18
Q
Ite has…
A
Less oxygen than ate
19
Q
Ide…
A
Has no oxygen except OH-
20
Q
What’s the formula for NO3
A
Mg(No3)2
21
Q
Derive the formula for Aluminium sulphate
A
Al2(SO4)3
22
Q
Why is the octet rule not perfect
A
Many exceptions
23
Q
2 types of bonding
A
Ironic and covalent
24
Q
Ironic bond
A
The attraction between positively charged and negatively charged ions after these ions wer formed by their low or gain of electrons
25
Whee on the PTE do ionic bomds usually form and why
Usually in groups 1,2,6 and 7
| Because these are elements which lose or gain electrons easily
26
Why do ionic compounds arrange themselves into?
Into regular rigid crystalline lattices
27
What is the simplest crystalline lattice?
Sodium chloride (NaCl)
28
Electronegativity difference of an ionic compound
Greater than 1.7
29
Show the electronic structure of magnesium fluoride and then give its structure
Ionic
| MgF2
30
Covalent bonding
A bond which is formed by the sharing of electrons to obey the octet rule
31
Electronegativity difference of covalent bond
1.7 or less
32
Generally, compounds containing non-metals only...
Take part in covalent bomd8;g
33
Show the electronic structure of the simplest compound between phosphorus and chlorine and give it’s formula
Covalent
| PCl3
34
Show the electronic structure and give the formula of the simplest compound between nitrogen and hydrogen
Covalent
| NH3
35
Show the electronic structure and give the formula of the simplest molecule of 2 chlorine atoms
Covalent
| Cl2
36
Show the electronic structure and give the formula of 2 oxygen atoms
O2
37
Show the electronic structure and give the formula of 2 nitrogen atoms
N2
38
Valency
The number or bond that an atom of an element forms when it reacts
39
Valency of 1,2,3,4
1,2,3,4
40
Valency of 5,6,7,8
8-group Number
| 3,2,1,0
41
Rule used to find the valencies of compound
The totals of the valencies of each element in the formula must be equal
Must be written in simplest ratio
42
Find the formula of calcium oxide using valencies
Ratio of 1:1
| CaO
43
Find the formula for the compound between germanium and hydrogen using valencies
Ratio 1:4
| GeH4
44
The valency of a complex ion is...
The charge of the complex ion
45
Use valencies to write the formula for calcium nitrate
Ratio 2:1
| Ca(NO3-)2
46
Transition elements, referring to valencies
Can have a number of valencies (variable valencies)
47
How do we know the valency of the transition metal in a question
Given by Roman numbers eg. Cu (II)
48
Use valencies to form the formula of manganese (IV) oxide
Ratio 2:1
| MnO2
49
4 properties of ionic compounds
* Usually hard and brittle solids
* High m.p and b.p
* Majority are soluble in water with ions moving apart (disassociation)
* Conduct electricity in molten state or aqueous solution (ions are free to move and carry charges with them
50
4 properties of covalent compounds
Usually gases, liquids or soft solids
Low m.p and b.p
Most are insoluble in water
Don’t conduct electricity (no ions present to carry charge)
51
Non polar covalent bond
Where pairs of electrons are shared equally between the atoms in a bond
52
Example of non polar covalent compound
O2
53
Polar covalent compound
Pairs of electrons are not shared equally between atoms in a bond
54
Example of polar covalent bond
HCl
55
In HCl, a polar covalent bond, the pairs of electrons are pulled closer to Cl than H, giving Cl a...
Partial negative charge
56
In HCl, a polar covalent bond, the pairs of electrons are pulled closer to Cl than H, giving H a...
Partial positive charge
57
Polar covalent bonds are due to...
Differences in electronegativity between the elements
58
In the PTE, across a period, electronegativity
Increases
59
In the PTE down a group, the electronegativity
Decreases
60
Why does the electronegativity increase across the PTE
Increasing nuclear charge makes it easier to attract a pair
| Decreasing atomic radius, electrons nearer the nucleus
61
Why does electronegativity decrease down the PTE
Extra levels of electrons=more screening
Increase in atomic radius
(Increasing nuclear charge cancelled out by^^)
62
EN difference greater than 1.7
Ionic
63
EN difference between 1.7 and 0.4
Polar covalent
64
EN difference less than 0.r
Non-polar covalent
65
Dipole moment
The ability of a molecule to turn in an electric field
66
When can molecules with polar covalent bonds make up a non polar covalent molecule
When the centres of positive and negative charge coincide
67
Why can molecules with polar covalent bonds make up a non polar covalent molecule when their centres of + and - charge coincide?
```
Charges cancel each other out
No overall charge
No dipole movement
Will not turn in an electric field
Not a polar covalent molecule
NON-POLAR COVALENT
```
68
Simple test to determine if a liquid is polar or non-polar
Note the effect of a charged plastic rod on a stream of liquid falling from a burette, if the liquid deflects, then it consists of polar molecules
69
Why would falling water be deflected towards a positively charged plastic rod
Water molecules are polar covalent and their partial negative charges cause them to be deflected towards positively charged rod
70
What happens with the water if a positive plastic rod is switched with a negatively charged plastic rod
Water molecules rearrange themselves so that the partial positive charges are deflected towards the negative rod.
Water is still deflected towards it,
71
At the level of atomic orbitals, what does a covalent bond consists of?
2 half full atomic orbitals
72
2 half full atomic orbitals overlapping into each other forms a
Molecular orbitals containing 2 shared electrons
73
Sigma bond
Head on overlapping
74
Double covalent bonds consist of
1 sigma bond and 1 pi bond
75
Pi bonds
Overlap sideways
76
Which bond is stronger sigma or pi and why
Sigma because there is more overlapping
77
Why in a double bond isn’t there 2 sigma bonds
Orbitals at 90°, a second sigma bond would break the first one
78
A triple covalent bonds is made up of
1 sigma bond
| 2 pi bonds
79
Why is a O=O bone not twice as strong as a O-O bond?
Because sigma bonds are stronger than pi bonds and the second bond in that molecule is a pi bond
80
Recrystallization
Technique used to purify certain crystalline substances
81
Melting point determination
Used to find out how pure a substance is
82
Certain substances are more soluble ...
In hot solvent than cold solvent
83
Benzodiazepines acid crystals are very soluble in
Hoy water but only slightly soluble in cold water
84
Why is it important to use minimal water in purifying benzoic acid experiment
Saturated solution needed
| Too much water, crystallization won’t occur
85
Why do u have to do the benxoic acid crystal experiment quickly
To prevent recrystallization occurring on the filter paper when filtering charcoal
86
Impurity’s consist of both..
Soluble and insoluble ones
87
What speeds up recrystalisation
Scraping the inside of the flask with a glass rod
88
Air suction device in second filtration
Büchner funnel
89
Why is a Büchner funnel used
To speed up process
90
Why would you wash last bit of benzoic acid crystals before taking them out of filter paper?
Still damp, that water could be contaminated with NaCl
91
Covalent bonds soluble
Only in hot water
92
Ionic bonds soluble in
Any water
93
Benzoic acid type of bond
Covalent
94
What do benzoic acid crystals look like?
White crystals
95
What is benzoic acid used for
Food preservative
96
Melting point of benzoic acid
122°C
97
Melting point determination
Determines how pure a substance is
98
How would you gather a sample of benzoic acid crystals in a capillary tube?
Gently push and rotate the open end of the tube into the crystals and take out, tap with fingernail to get the to the bottom
Repeat until 1cm of crystals in tube
99
Impure if 2
Melt over large range eg 6°
| Melt at a lower melting point to the crystals average
100
2 uses for melting point determination
Check purity
| Identify a substance
