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Chemical Bonding.2 Flashcards

1
Q

What is a compound

A

substance made up of two or more elements chemically combined

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2
Q

what is the octet rule?

A

When bonding occours, atoms tend to reach an electron arrangement with eight electrons in the outermost shell

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3
Q

What are expections to the Octet rule

A

Transition elements dont obey the octet rule and often have more or less than 8 electrons in the outer shell
Elements near helium tens to have 2 electrons in the outer shell

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4
Q

What is ment by the valency of an element

A

the valency of an element js the number of atoms of hydrogen in which an atom of the element can bond

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5
Q

Variable valancy

A

the number of atoms of different elements in which a certain element can combine with.

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6
Q

What is an ion

A

A charged atom/ group of atoms

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7
Q

What is a postive ion called

A

Cations

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8
Q

What is a negative ion called

A

Anions

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9
Q

What is the valency of an ion equal to?

A

its charge

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10
Q

What are the two types of bonding

A

Ionic boning
Covalent bonding

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11
Q

Define an ionic bond

A

The electrostatic attraction between a postive and negative ion.

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12
Q

What do you use to show the formation of ionic bonding

A

Bohr diagrams, dot and cross diagrams

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13
Q

Comment of the structure of ionic compounds

A

crystal lattice structure ( ionic compounds do not form individual molecules )

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14
Q

Discuss the melting and boiling points of ionic compounds

A

Very high melting and boiling points - the electrostatic attractions require a lot of energy to be broken

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15
Q

Discuss the apperance of ionic compounds

A

exist as solid crystalline structures.
Most ionic compounds are white

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16
Q

Discuss the conduction of electricity of ionic compounds

A

do not conduct electricity in the solid state are ions are not free to move- held in a crystal lattice structure.
Will conduct electricity when molten or dissolved- ions- free to move

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17
Q

Give three uses of ionic compounds

A

Sodium chloride- essential in diet
salt used on food as preservative
hydrated sodium carbonate- washing soda tablets- clean clothes- remove hardness from water

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18
Q

Define a covalent bond

A

bond that forms when two atoms share a pair of electrons

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19
Q

what is a molecule

A

two or more atoms chemically combined

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20
Q

Discuss the melthing and boiling point of covalent compounds

A

low melting and boiling points - weak intermolecular forces between covelent molecules

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21
Q

Discuss the apperance at room temp of covalent compounds

A

most covelent molecules are liquids or gasses and solids are soft in apperance

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22
Q

Discuss the conduction of electricity of covalent compounds

A

will NOT conduct electriity as there are no ions avliable

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23
Q

Atomic orbital

A

region in space around the nucleus where there is a high probability of finding and electrons.

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24
Q

What is a sigma bond

A

head on overlap of two orbitals

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25
What is a pi bond
sideways overlap of p or d orbitals
26
Are Sigma bonds stronger or Pi bonds stronger
There is less overlap between orbitals in a pi bond, therefore it is weaker than a sigma bond
27
What does a single covalent bond consist of
1 sigma bond
28
What does a double covalent bond consist of
1 sigma and 1 pi bond
29
What does a triple covalent bond consist of
1 sigma and two pi
30
Give two differences between sigma bonds and pi bonds
**Sigma bonds** formed by the head on overlap of atomic orbitals Stronger bonds- not easily broken *Pi bonds* sideways overlap of p or d orbitals weaker bonds- more easily broken
31
Electronegativity
the measure of relative attraction that an atom has for a shared pair of electrons
32
What is a charge indicted by?
Delta δ
33
Name the two types of covalent bond
Non-polar covalent bond (pure covalent) Polar covalent bond
34
what is a non-polar covalent bond (pure covalent) name an example
type of bond that forms when two atoms share a pair of electrons equally. e.g Cl2
35
What is a polar covalent bond. Name an example e.g HCl
type of bond that formes when two atoms share a pair of electrons unequally
36
Why are the electrons shared equally in non-polar covalent bonding
The differnce in electronegativity values involved is 0 or so small that the shared pair of electrons are shared equally
37
why are the electrons shared unequally in polar covalent bonding
the difference in electronegativity calues in the elemets is significant so the pair of electrons are pulled towards the more electronegative atom, are shared unequally.
38
What can electronegivity be used to predict
Polarity of covalent bonds perdict which compounds are ionic and which ones are covalent
39
What does a EN difference of >1.7 indicate?
Ionic bonding
40
What does a EN difference of 0.4 -1.7 indicate?
Polar Covalent bond
41
What does a EN difference of < (or equal) 0.4 indicate?
Non polar covalent bond
42
What is the significance of a molecule having polar covalent bonds
the more electronegative atom acquired a partially negative charge / negative diople the less electronegative atom acquires a partially postive charge/ postive dipole
43
what is the electronegativity differnce of non-polar covalent bonding?
0-0.39
44
what is the electronegativity differnce of polar covalent bonding
0.4- 1.69
45
what is the electronegativity differnce of od Ionic bonding
1.7 <
46
what two compounds are expections to the electronegativity rules
Boron trifluoride (BF3) Hydrogen fluoride (HF) you think they would have ionic bonding but they actually have polar colvalent bonding
47
What is the demostrating polarity used to show
to show if a compund (usually a liquid)is polar.Water is polar. ( has tempoary postive charges associated) water will deflect when a postively or negativily charged rod comes near. The H postive will be attracted towards the negativily charged rod.Similarly, the O (negative) will be sttracted to th negativitly charged rod. ***Cyclohexane is an organic compound that is non-polar (no deflection)***
48
In the demostating polarity, explain why a polar liquid will also be attracted to a rod regardless of if the rod is charged, negativily or postively.
the polar molecules in the liquid will turn and arrange themselves so.. for a negatively charged rod- the postive dipoles will be attracted to it. for a postively charged rod- the negative dipoles of the molecule will be attracted
49
Whats does VSEPRT stand for
Valence shell electron pair replusion theory
50
what is VSEPRT used for
to perdict the same of a molecule
51
what does the shape of a molecule depend on?
the number of pairs of electrons in the valence shell of the central atom. the type of these pairs (Bond pair or lone pair)
52
Describe VSEPRT
This theory is used to perdict the shape of a molecule. The shape of a molecule depends on the number of pair of electrons in the valence shell of the central atom, and the type of these pairs. electron pairs repel eachother. A lone pair and lone pair of electrons (stongest )repel each other more strongly than a lone pair and bond pair of electrons (moderate )which repel each other more strongly than a bond pair and bond pair of electrons (weakest)
53
What is a loan pair
Both electrons come from the same atom
54
What is a bond pair of electrons
each electron comes from a different atom
55
What is a dative corrdinate bond
Special type of covalent bond where one atom supplies both the electrons Eg. NH4+
56
A molecule has 4 electron pairs,4 bond pairs,0 loan pairs what shape it it?
Tetrahedral
57
A molecule has 3 electron pairs,3 bond pairs,0 loan pairs what shape it it?
Trigonal planer
58
A molecule has 2 electron pairs,2 bond pairs,0 loan pairs what shape it it?
Linear
59
A molecule has 4 electron pairs,3 bond pairs,1 loan pairs what shape it it?
Pyramidial
60
A molecule has 4 electron pairs,2 bond pairs,2 loan pairs what shape it it?
V-shaped / bend
61
What is the bond angle of a tetrahedral
109.5
62
What is the bond angle of a trigonal planer
120
63
What is the bond angle of a linear
180
64
What is the bond angle of a pymidial
107
65
What is the bond angle of a v-shaped
104.5
66
Which molecule shapes are not symmetrical
Pyramidial and v-shaped
67
What type of molecule does VSEPRT only apply to
covalent molecule
68
Explain why certain molecules can be non-polar molecules despite having polar bonds within their molecule
If the molecule is highly symmetrical the centres of postive and negative charge coincide the molecule as a whole is non polar despite having polar bonds.
69
Distinguish between intramolecular bonds and intermolecular forces
Intramolecular bonds- Type of bond **inside** the molecule Intermolecular bond - forces of attraction that exist between one molecule and another
70
Name the three types of intermolecular forces
Van der waals Dipole-Dipole Hydrogen bonding
71
Describe Van der waals
between a non-polar molecule and another non-polar molecule- caused by tempoary dipoles formedin the atoms. Low melthing and boiling points- gas at room temp. As the molecules molecular mass increases, the stenght of the van der waals increases.
72
describe Dipole-Dipole forces
form between polar molecules- caused by permanent dipoles in the atoms. partially pos atom attracted to partially neg atom. Stronger than van der Waals forces
73
describe Hydrogen Bonding
attaction between a partially postive hydrogen in one molecule and a partially negative N,O or F in another molecule. Strongest intermolecular forces
74
Why does hydrogen bonding only occur between molecules with partially negative nitrogen, oxygen, or fluorine atoms?
Nitrogen, oxygen and fluorine are small and highly electronegative atoms
75
Give three effects of hydrogen bonding
explains why the three hydrides H2), hf and nH3 have higher boiling points than other hydrides explais how H2O has a very large relative boiling point explains surface thension on water
76
Hydrogen bonding in everyday life
Ensures water is liquid at room temp so life can exist on earth. Synthetic clothing- bullet proof vests/protective clothing. hydrogen bonds in wool help it absorb water. hydrogen bonds in water give it a high surface tension.
77
How to compare boiling points of different substances
CHECK: 1 - type of intermolecular force...hydrogen stronger than dipole-dipole stonger than Van der waals 2 - the molecular mass of the molecule....heavier molecules have higher boiling points 3 - how polar the molecule is... more polar molecules have higher boiling points
78
compare the solubilities of ionic compounds in water
ionic compounds are very soluble in water the partial negative charge in the polar water is attreacted to the postive ion in the ionoc compound the partial postive charge in the polar water is sttracted to the negative ion in the ionic compounds. The crystalline structure can be pulled apart
79
compare the solubilities of ionic compounds in cytohexane
ionic compounds are not soluble in non-polar solvents. No partial charges in the non polar solvent to pull the ionic crystal apart
80
General rule for dissolving substances
Like dissolves like
81
Explain why ammonia is readily soluble in water?
water molecules are polar, amonia molecules are polar hydrogen bonds form between the molecules and ammonia dissoves
82
Would you expect iodine to be soluble in water? Explain
Iodine is not soluble/sparingly soluble in water Iodine molecules are non-polar, water molecules are polar Little or no Intermolecular forces form between the molecules, so the iodine does not dissolve

Chemistry (35 decks)

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