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Chemistry > Chemical Bonding.2 > Flashcards

Chemical Bonding.2 Flashcards

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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
Q

What is a pi bond

A

sideways overlap of p or d orbitals

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26
Q

Are Sigma bonds stronger or Pi bonds stronger

A

There is less overlap between orbitals in a pi bond, therefore it is weaker than a sigma bond

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27
Q

What does a single covalent bond consist of

A

1 sigma bond

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28
Q

What does a double covalent bond consist of

A

1 sigma and 1 pi bond

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29
Q

What does a triple covalent bond consist of

A

1 sigma and two pi

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30
Q

Give two differences between sigma bonds and pi bonds

A

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

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31
Q

Electronegativity

A

the measure of relative attraction that an atom has for a shared pair of electrons

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32
Q

What is a charge indicted by?

A

Delta δ

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33
Q

Name the two types of covalent bond

A

Non-polar covalent bond (pure covalent)
Polar covalent bond

34
Q

what is a non-polar covalent bond (pure covalent) name an example

A

type of bond that forms when two atoms share a pair of electrons equally.
e.g Cl2

35
Q

What is a polar covalent bond. Name an example
e.g HCl

A

type of bond that formes when two atoms share a pair of electrons unequally

36
Q

Why are the electrons shared equally in non-polar covalent bonding

A

The differnce in electronegativity values involved is 0 or so small that the shared pair of electrons are shared equally

37
Q

why are the electrons shared unequally in polar covalent bonding

A

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
Q

What can electronegivity be used to predict

A

Polarity of covalent bonds
perdict which compounds are ionic and which ones are covalent

39
Q

What does a EN difference of >1.7 indicate?

A

Ionic bonding

40
Q

What does a EN difference of 0.4 -1.7 indicate?

A

Polar Covalent bond

41
Q

What does a EN difference of < (or equal) 0.4 indicate?

A

Non polar covalent bond

42
Q

What is the significance of a molecule having polar covalent bonds

A

the more electronegative atom acquired a partially negative charge / negative diople
the less electronegative atom acquires a partially postive charge/ postive dipole

43
Q

what is the electronegativity differnce of non-polar covalent bonding?

A

0-0.39

44
Q

what is the electronegativity differnce of polar covalent bonding

A

0.4- 1.69

45
Q

what is the electronegativity differnce of od Ionic bonding

A

1.7 <

46
Q

what two compounds are expections to the electronegativity rules

A

Boron trifluoride (BF3)
Hydrogen fluoride (HF)

you think they would have ionic bonding but they actually have polar colvalent bonding

47
Q

What is the demostrating polarity used to show

A

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
Q

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.

A

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
Q

Whats does VSEPRT stand for

A

Valence shell electron pair replusion theory

50
Q

what is VSEPRT used for

A

to perdict the same of a molecule

51
Q

what does the shape of a molecule depend on?

A

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
Q

Describe VSEPRT

A

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
Q

What is a loan pair

A

Both electrons come from the same atom

54
Q

What is a bond pair of electrons

A

each electron comes from a different atom

55
Q

What is a dative corrdinate bond

A

Special type of covalent bond where one atom supplies both the electrons
Eg. NH4+

56
Q

A molecule has 4 electron pairs,4 bond pairs,0 loan pairs what shape it it?

A

Tetrahedral

57
Q

A molecule has 3 electron pairs,3 bond pairs,0 loan pairs what shape it it?

A

Trigonal planer

58
Q

A molecule has 2 electron pairs,2 bond pairs,0 loan pairs what shape it it?

A

Linear

59
Q

A molecule has 4 electron pairs,3 bond pairs,1 loan pairs what shape it it?

A

Pyramidial

60
Q

A molecule has 4 electron pairs,2 bond pairs,2 loan pairs what shape it it?

A

V-shaped / bend

61
Q

What is the bond angle of a tetrahedral

A

109.5

62
Q

What is the bond angle of a trigonal planer

A

120

63
Q

What is the bond angle of a linear

A

180

64
Q

What is the bond angle of a pymidial

A

107

65
Q

What is the bond angle of a v-shaped

A

104.5

66
Q

Which molecule shapes are not symmetrical

A

Pyramidial and v-shaped

67
Q

What type of molecule does VSEPRT only apply to

A

covalent molecule

68
Q

Explain why certain molecules can be non-polar molecules despite having polar bonds within their molecule

A

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
Q

Distinguish between intramolecular bonds and intermolecular forces

A

Intramolecular bonds- Type of bond inside the molecule
Intermolecular bond - forces of attraction that exist between one molecule and another

70
Q

Name the three types of intermolecular forces

A

Van der waals
Dipole-Dipole
Hydrogen bonding

71
Q

Describe Van der waals

A

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
Q

describe Dipole-Dipole forces

A

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
Q

describe Hydrogen Bonding

A

attaction between a partially postive hydrogen in one molecule and a partially negative N,O or F in another molecule.
Strongest intermolecular forces

74
Q

Why does hydrogen bonding only occur between molecules with partially negative nitrogen, oxygen, or fluorine atoms?

A

Nitrogen, oxygen and fluorine are small and highly electronegative atoms

75
Q

Give three effects of hydrogen bonding

A

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
Q

Hydrogen bonding in everyday life

A

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
Q

How to compare boiling points of different substances

A

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
Q

compare the solubilities of ionic compounds in water

A

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
Q

compare the solubilities of ionic compounds in cytohexane

A

ionic compounds are not soluble in non-polar solvents. No partial charges in the non polar solvent to pull the ionic crystal apart

80
Q

General rule for dissolving substances

A

Like dissolves like

81
Q

Explain why ammonia is readily soluble in water?

A

water molecules are polar, amonia molecules are polar
hydrogen bonds form between the molecules and ammonia dissoves

82
Q

Would you expect iodine to be soluble in water? Explain

A

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 (27 decks)

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