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A Level Chemistry-CIE > Chemical Bonding > Flashcards

Chemical Bonding Flashcards

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1
Q

What is ionic bonding?

A

Electrostatic attraction between cation and anion is called an ionic bond or an electrovalent bond.

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2
Q

What is the state of matter of ionic compounds at room temperature and pressure?

A

ionic compounds are solids room temperature and pressure.

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3
Q

Are ionic compounds volatile?

A

Ionic compounds are non volatile. Don’t evaporate at room temperature room temperature.

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4
Q

Do ionic compounds have low or high melting and boiling points?

A

Due to strong electrostatic attraction compounds have high melting and boiling points.

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5
Q

Do ionic compounds conduct electricity in the solid state?

A

Due to the absence of free mobile ions ionic compounds cannot conduct electricity in the solid state.

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6
Q

Do ionic compounds conduct electricity in the aqueous or molten state.

A

Due to the presence of free mobile ions ionic compounds do conduct electricity in the aqueous or molten state.

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7
Q

Are ionic compounds water soluble?

A

Ionic compounds are water soluble except Al2O3 and MgO. (because MgO and Al2O3 have a giant ionic lattice structure which dose not break easily and so they do not dissolve easily.

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8
Q

Define charge density.

A

Charge density is equal to charge/volume OR charge/Radius.

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9
Q

What is meant by the polarising power of a cation?

A

The ability of cations to attract or distort the electron cloud of anion is called the polarising power of a cation.

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10
Q

What does the polarising power of a cation depend upon?

A

The polarising power of a cation depends upon charge density. The greater the charge density the stronger the polarising power of cation.

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11
Q

Define covalent bonding:

A

A covalent bond involves the electrostatic attraction between nuclei of two atoms and a shared pair of electrons. Covalent bonding occurs between two non metals.

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12
Q

Is ionic bond formation an exothermic or endothermic process?

A

Ionic bond formation is an exothermic process.

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13
Q

What is the formula for nitrate ion?

A

NO3-

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14
Q

What is the formula for a Sulphate ion?

A

SO4^3-

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15
Q

What is the formula for Carbonate Ion?

A

CO3^2–

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16
Q

What is the formula for an ammonium ion?

A

NH4+

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17
Q

What is the formula for a hydroxide ion?

A

OH-

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18
Q

What is the formula for a Phosphate ion?

A

PO4^3-

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19
Q

What is a lone pair of electrons?

A

A lone pair of electrons refers to a pair of electrons that are not shared with another atom in a covalent bond and is sometimes called unshaired pair or non bonding pair.

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20
Q

Which elements have lone pairs?

A

The elements of group 5,6 and 7 have lone pair of electrons in their molecules.

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21
Q

What is the significance of a lone pair of electrons?

A

1.Affect the shape of covalent molecules.
2.Forms Dative bonding.
3.Are involved in hydrogen bonding.
4. Are important in the chemical reactions of compounds such as water and ammonia.

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22
Q

What is an electron deficient atoms?

A

There are some molecules which accommodate less than eight electrons in the outer shell which means that the central atom is “electron deficient”. For example boron trifluoride BF3 has only six electrons around the boron atom meaning that it is electron deficient.

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23
Q

What is an expanded octet atoms?

A

There are some molecules which accommodate more than eight electrons in their outer shell which means that the central atom is an expanded octet. (Mostly the elements in the period 3 can expand their octet. These elements use their unfilled empty 3p or 3d orbitals for the extra electrons. For example sulphur dioxide.

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24
Q

What is coordinate or dative bonding?

A

A coordinate or dative bond is a covalent bond (a shared pair of electrons) in which both electrons come from the same atom.

Some molecules have a lone pair of electrons that can be donated to form a bond with an electron deficient atom.

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25
Q

How does a dative or coordinate bond differ from a covalent bond?

A

A coordinate bond only differs from a covalent bond in its formation. Once formed it behaves just like a covalent bond.

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26
Q

Define metallic bonding.

A

A metallic bond is the electrostatic force of attraction between the positive metals ions and a sea of delocalised electrons.

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27
Q

What is an alloy.

A

Metals form alloys. Alloys are a mixture of metals and contain only metallic bonding. Alloys are stronger than metals.

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28
Q

REVIEW VALENCE SHELL ELECTRON PAIR REPULSION THEORY.

A
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29
Q

What is bond energy?

A

Bond energy (also known as bond enthalpy) is the energy required to break one mole of a particular covalent bond in the gaseous state.

as bond length increases bond energy decreases.

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30
Q

What are the units of bond energy?

A

The units are kilojoules per mole, KJ mol-1.

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31
Q

What is Bond Length?

A

Bond Length is the distance between the nuclei of two covalent bonded atoms.

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32
Q

What is the effect of bond strength?

A

Bond Strength can influence the reactivity of a compound.

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33
Q

What is hybridisation?

A

The mixing of atomic orbitals (with different energy shapes) to give a set of hybrid orbitals with the same energy and shape is called hybridisation.

34
Q

With respect to atomic orbitals what are the two type of covalent bonds?

A

Sigma bonds and Pi bonds.

35
Q

How are sigma bonds formed?

A

Sigma bonds are formed from head to head (end to end) overlap of orbitals.σ

36
Q

Where does the electron density lie for sigma bonds?

A

e- density lies on the axis connecting the two nuclei.

37
Q

Why is sigma a strong bond?

A

Sigma bond is a strong bond as orbitals overlap to the maximum extent.

38
Q

Is rotation possible around a sigma bond?

A

Rotation is possible around a sigma bond.

39
Q

What are the types of sigma bonds?

A

There are three different types of sigma bonds:

s-s overlap
p-s overlap
p-p overlap

40
Q

How is a pi bond formed?

A

Pi bond is always formed throgh sideways (parallel) p-orbitals overlapping/

41
Q

Why is a pi bond weak?

A

Orbitals don’t overlap to the maximum extent which is why pi bonds are weaker than sigma bond.

42
Q

Where does electron density lie in a pi bond?

A

Electron density lies above and below the axis containing the two nuclei.

43
Q

Is rotation possible around a pi bond.

A

Rotation is not possible around a pi bond.

44
Q

When does the process of hybridisation take place?

A

The process of hybridisation takes place at the time of bonding.

45
Q

What are the rules to follow when considering hybridisation?

A

There are three types of hybridisation: SP3 SP2 SP

When considering hybridisation always consider double and triple bonds as single.

46
Q

Explain tetrahedral hybridisation.

A

SP3
4 single bonds
Tetrahedral
109.5°
e.g.CH4,C2H6

47
Q

Explain trigonal pyramidal hybridisation.

A

SP3
3 single bonds
1 lone pair
Trigonal Pyramidal
107°
e.g. NH3

48
Q

Explain trigonal planar hybridisation.

A

SP2
3 single bonds
0 lone pair
Trigonal Planar
120°
e.g. ALCL3 C2H4

49
Q

Explain linear hybridisation.

A

SP
2 single bonds
0 lone pairs
Linear
180°
e.g. BeCl2

50
Q

Explain Bent or non linear hybridisation.

A

SP3
2 single bonds
2 lone pairs or 1 lone pairs
bent or non-linear
104.5° 2 lone pairs e.g. H20
117° 1 lone pairs

51
Q

Define electronegativity.

A

Electronegativity is the ability of an atom in a covalent bond to attract a shared pair of electrons towards itself.

52
Q

What is a dipole and how it is used?

A

The more electronegative electron gets δ- (partial negative) while the less electronegative electron gets δ+ (partia positive).

53
Q

What is electronegativity measured in?

A

Electronegativity is measured on the Pauling’s scale. (ranges from 0 to 4).

54
Q

What is a dimer, give examples of dimers.

A

a dimer is a polymer formed from two molecules of a monomer. Al2Cl6 and BeCl2 is a dimer with coordinate bonds.

55
Q

What are the most electronegative elements?

A

The most electronegative elements can be remembered by FONCL. Fluorine is the most electronegative element.

56
Q

Describe the trend in electronegativity across a period.

A

Electronegativity increases across a period. This is because the number of protons increase.

57
Q

Describe the trend of electronegativity as you go down a group.

A

Electronegativity decreases as you go down a group. This is because the smaller atoms are less shielded, the nucleus is more exposed so has greater attraction for the electrons.

58
Q

What is the hybridisation of alkenes?

A

All alkenes have sp2 hybridisation.

59
Q

What is a non-polar covalent bond?

A

A non polar covalent bond is formed when there is no difference in electronegativity or the dipoles cancel out.

60
Q

What are non-polar covalent molecules held by?

A

Non polar covalent molecules are held together by van der wall forces.

61
Q

What is a polar covalent molecule?

A

A polar covalent molecule is formed when electrons in a bond are unequally shared resulting in δ- and δ+ charges.

62
Q

Describe the electron distribution in a polar covalent molecule.

A

In polar covalent molecules we say that the electron configuration is asymmetrical.

63
Q

What is a dipole moment?

A

The degree of polarity is measured as a dipole moment. The direction of the dipole is shown by the sign ↦. The arrow points towards the partially negative charged end of the dipole.

64
Q

Are all molecules with polar bonds, polar molecules?

A

Not all molecules with polar bonds are polar molecules. Some times the polar bonds cancel each other out because the same types of bonds have dipoles pulling them in opposite directions.

65
Q

Define bond polarity

A

Bond polarity is the partial separation of charge when two different atoms are joined by a covalent bond. This results in an unequal attraction for the bonding pairs of electrons.

66
Q

Which shapes are non-polar?

A

Symmetrical shapes are non polar and have zero dipole moment.
These are the following symmetrical shapes:
*Tetrahedral
*Trigonal Planar
*Linear shaped molecules

67
Q

What are intermolecular forces of attraction?

A

Intermolecular forces are the attractive forces of attraction which exist between molecules, do not mistake with the actual bond. The bond will be covalent, ionic or metallic.

68
Q

Which properties depend upon intermolecular forces?

A
  • The states of matter
    *Melting and boiling points
    *solubility of substances
    *Surface tension
    *Viscosity
69
Q

Define surface tension

A

Surface tension is defines as the property of the surface of liquid to resist an external force due to the cohesive nature of water.

70
Q

What are the types of inter molecular forces?

A

*hydrogen bonding
*permanent dipole-permanent dipole interaction’s
*London dispersion forces/temporary induced dipole-dipole interactions/ instantaneous dipole-dipole forces

71
Q

What is hydrogen bonding?

A

Hydrogen bonding is the electrostatic attraction between more electronegative elements and hydrogen atoms. if hydrogen is covalently bonded with the more electronegative element along with a loan pair then hydrogen bonding takes place

72
Q

Which molecules have hydrogen bonding?

A
  • All aldehydes dot have hydrogen bonding
    *All ketones don’t have hydrogen bonding
  • All esters don’t have3 hydrogen bonding
    *All alcohols and carboxylic acids have hydrogen bonding.
73
Q

When does permenant dipole-dipole interactions occur?

A

Polar molecules have permenant dipoles.

74
Q

Describe the strength of a permanent dipole-dipole interactions.

A

Permanent dipoles are stronger than induced dipole-dipole force. Their force also depends upon shape of molecule as well.

75
Q

How does temporary dipole-dipole force occur?

A

In any molecule the electrons are moving constantly and randomly. At any instance the electron clod may become distorted or unsymmetrical which would give rise to an instantaneous dipole.

These temporary dipoles can induce dipoles to form in neighbouring molecules called induced dipole.

76
Q

Which molecules have temporary dipole-dipole force?

A

They are present in all molecules but are usually only considered when other type of intermolecular forces are absent. (non-polar and noble gases)

77
Q

What are the factors affecting van der wall forces.

A

No of electrons/Bigger size/Larger Mr

as the electron, Mr and size increase so does the boiling point of the molecule.

In Alkanes and Alkenes , he shape of the molecule can have effect.

The long/straight chains have large surface area of contact between molecules for London forces to form.

78
Q

How do we draw a diagram which involves hydrogen bonding?

A

Always show lone pair
Always show dipoles
Always form hydrogen bond in direction of lone pair
The bond angle is 180° around the H atom

79
Q

What are the properties of compounds with hydrogen bonding?

A

High melting and boiling point
Soluble in other compounds with hydrogen bonding.

80
Q

What are the unusual properties of water due to hydrogen bonding?

A

Decrease in density when water freezes i.e the density of water is higher than ice.
Water behaves as an excellent solvent (ionic substances)

81
Q

Define an allotrope.

A

An allotrope is different physical forms of the same element in the physical state.

82
Q

What are the allotropes of carbon?

A

Diamond
Graphite
Graphene
Fullerene

A Level Chemistry-CIE (13 decks)

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