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Chemistry A level > Bonding > Flashcards

Bonding Flashcards

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1
Q

Definition of ionic bonding?

A

Electrostatic attraction between positive and negative ions

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2
Q

In general where do you find ionic bonding?

A

Compounds made up of a metal and a non metal

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3
Q

How to draw ionic dot and cross diagrams?

A

Metal: Put symbol in brackets, and it’s charge in the top right

Non metal: Put symbol surrounded by outer shell showing which electrons are from which element, inside the brackets. Then put the charge at the top right

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4
Q

Definition of a covalent bond?

A

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

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5
Q

What’s a molecule?

A

A small group of atoms bonded together by covalent bonds

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6
Q

How to draw covalent molecule dot and cross diagrams?

A

Look at group number to determine how many electrons in outer shell of each element

Pair up unpaired electrons between atoms to form covalent bonds, using different symbols for each atoms electrons

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7
Q

How many electrons are in the outer shell of atoms after forming covalent bonds (ignoring hydrogen)?

A

8, the octet rule

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8
Q

What’s a covalent double bond?

A

Made up of 2 shared pairs of electrons

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9
Q

What’s a covalent triple bond?

A

Made up of 3 shared pairs of electrons

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10
Q

What’s a shared pair of electrons called?

A

A bonding pair

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11
Q

What’s a pair of electrons in the outer which aren’t being used in bonding called?

A

A lone pair

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12
Q

What’s a dative covalent bond?

A

A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only

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13
Q

If there’s a dative bond what charge will be on the molecule?

A

A positive one, as an electron has been lost

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14
Q

What’s the definition of average bond enthalpy?

A

The average enthalpy change which takes place, when breaking by homolytic fission one mole of a given type of bond in the molecules of a gaseous species

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15
Q

What’s the relationship between average bond enthalpy change and the strength of the covalent bond?

A

A stronger bond will have a larger average bond enthalpy

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16
Q

What’s stronger a double or a single bond?

A

Double

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17
Q

What type of structure do metals have?

A

Giant- continuous structure in three dimensions

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18
Q

In metals why are the electrons in their valence shells held loosely?

A

Metals have relatively low ionisation energies, so metals are surrounded by delocalised electrons

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19
Q

What’s the general structure of a metal?

A

Lattice of positive ions, surrounded by a delocalised sea of electrons

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20
Q

Definition of metallic bonding?

A

The electrostatic attraction between positive metal ions and delocalised electrons

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21
Q

Why do metals have high melting and boiling points?

A

Strong electrostatic attraction between positive metal ions and delocalised electrons requires a lot of energy to break

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22
Q

why are metals Good conductors of electricity when solid?

A

Delocalised electrons can move and carry charge

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23
Q

why are metals Good conductors of electricity when molten?

A

Delocalised electrons and positive ions can move and carry charge

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24
Q

Why are metals insoluble in water or non polar solvents?

A

Strong electrostatic attractions between positive ions and delocalised electrons require a lot of energy to break, which isn’t available

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25
Q

How many electrons in metals or donated into the sea of electrons?

A

All of them, so as you go up the groups more electrons are donated

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26
Q

Why does the melting points of period 3 metals increase as you go up the groups?

A

The charge of the metal ion increases, and the number of delocalised electron per ion increases as well, this means stronger electrostatic attraction between metal ions and delocalised electrons, so more energy required to break them

Also more delocalised electrons per ion, means better at conducting electricity, so has a greater capacity of carrying charge

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27
Q

Metals are malleable, what does that mean?

A

Can easily be bent in to different shapes

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28
Q

Metals are ductile, what does that mean?

A

Can be drawn into a wire

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29
Q

Why are metals ductile and malleable?

A

Layers of ions can easily slide over each other

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30
Q

What are alloys?

A

mixtures of metals

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31
Q

What metals are present in brass?

A

Cu and Zn

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32
Q

What metals are present in stainless steel?

A

Fe and Cr

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33
Q

How does an alloy make a metal harder?

A

Each metal ion is a slightly different size, so layers of ions do not slide over each other as easily

34
Q

What is the arrangement of ions in an ionic solid described as?

A

Giant ionic lattice

35
Q

What is a giant ionic lattice?

A

Continuous lattice arrangement of + and - ions in three dimensions

36
Q

Why do ionic compounds have high boiling and melting points?

A

Strong electrostatic forces of attraction between positive and negative ions requires a lot of energy to overcome

37
Q

Why are ionic compounds non conductors of electricity when solid?

A

The ions are fixed in lattice so cannot move and carry charge

38
Q

Why are ionic compounds good electricity conductors when molten or dissolved in water?

A

The ions are no longer fixed in lattice, so are able to move and carry charge

39
Q

Why do ionic compounds have good solubility in water?

A

Oxygen atom in water molecules is attracted to and surrounds the positive ions in the lattice, and the hydrogen atoms in the water molecules are attracted to and surround the negative ions. This breaks down the ionic lattice and dissolves the compound

40
Q

Why are ionic compounds brittle?

A

The slight movement of a layer of ions brings positive ions next to other positive ions, and the same for negative ions. This causes repulsion and the structure breaks apart

41
Q

Factors which lead to high melting points in ionic compounds?

A

Higher charges in ions

Small ionic radius

42
Q

What’s a simple molecular structure?

A

Small units containing a definite number of atoms, and a definite molecular formula

43
Q

Do simple molecular structure have a high or low melting/ boiling points and why?

A

Low, weak intermolecular forces between molecules require little energy to break

44
Q

Are simple molecular structure electrical conductors?

A

No, have no free mobile electrons or charged particles to carry charge

45
Q

What’s a giant covalent structure?

A

Billions of atoms held together to form a network of strong covalent bonds

46
Q

Do giant covalent structures have high or low melting/boiling points? Why?

A

High, Strong covalent bonds need to be broken, which requires a lot of energy

47
Q

Are giant covalent structures electrical conductors?

A

No, have no free mobile electrons or charged particles to carry charge

48
Q

Structure of diamond?

A

Each carbon forms 4 covalent bonds, making it very hard

49
Q

Is diamond an electrical conductor?

A

No, no free electrons to carry charge

50
Q

Is diamond hard?

A

Yes, tetrahedral structure of each carbon atom spreads force throughout the structure, strong covalent bonds require a lot of energy to break

51
Q

Structure of graphite?

A

Each carbon forms 3 covalent bonds, creating layers which are free to slide over each other

52
Q

Can graphite conduct electricity?

A

Yes, delocalised electrons in layers are free to move and carry charge

53
Q

Is graphite hard?

A

No, weak intermolecular forces between layers can be broken, and layers can slide over each other

54
Q

Why is graphite a good lubricant?

A

Strong layers but weak London forces between the layers which need little energy to break. The layers can slide over each other easily

55
Q

What does the valence shell electron pair repulsion theory state?

A

Electron pairs repel each other

The repulsion between lone pair- lone pair> to lone pair- bonded pair > bonded pair- bonded pair

56
Q

Features of a compound which has 2 bonded pairs around the central atom?

A

Orbital arrangement: Linear

Bond angle:180 degrees

57
Q

Features of a compound which has 3 bonded pairs around the central atom?

A

Orbital arrangement: Trigonal planar

Bond angle: 120 degrees

58
Q

Features of a compound which has 4 bonded pairs around the central atom?

A

Orbital arrangement: Tetrahedral

Bond angle 109.5 degrees

59
Q

Features of a compound which has 3 bonded pairs and 1 lone pair around the central atom?

A

Orbital arrangement: Trigonal Pyramid

Bond angle: 107 degrees

60
Q

Features of a compound which has 2 bonded pairs and 2 lone pairs around the central atom?

A

Orbital arrangement: V shaped or bent

Bond angle: 104.5

61
Q

Features of a compound which has 6 bonded pairs around the central atom?

A

Orbital arrangement: Octahedral

Bond angle: 90 degrees

62
Q

What does intermolecular forces mean?

A

Forces between molecules

63
Q

Where would you find intermolecular forces?

A

Simple covalent lattice

64
Q

What are the 2 types of van der waal forces?

A

London forces (induced dipole to dipole)

Permanent dipole-dipole interactions

65
Q

What’s the only attractive intermolecular force that acts in non polar molecules?

A

London forces

66
Q

How do London forces arise?

A

Electrons in molecules are constantly moving, at any instant the distribution may not be symmetrical, resulting in an instantaneous temporary dipole.

This dipole induces dipoles in neighbouring molecules, and leads to an attraction between neighbouring charges in the dipoles.

These attractions are London forces

67
Q

What’s a dipole?

A

a pair of equal and oppositely charged or magnetized poles separated by a distance

68
Q

What affects the strength of London forces?

A

The more electrons that are in the molecule, the stronger the fluctuations in the electron cloud, and the greater the instantaneous dipole to induced dipole forces

For molecules with the same amount of electrons, the greater the contact area between the molecules, the stronger the induced dipoles that develop. So unbranched molecules have stronger London forces than branched molecules, as there contact area is greater

69
Q

definition of electronegativity?

A

The ability of an atom to attract the bonding electrons in a covalent bond

70
Q

What are the elements with the largest electronegativity from highest to lowest and there pauling value?

A

F 4.0, O 3.5, N 3.0, Cl 3.0

71
Q

What is a permanent dipole?

A

A small charge difference which doesn’t change across a bond, with partial charges on the bonded atoms

72
Q

What’s a polar covalent bond?

A

A bond with a permanent dipole, having positive and negative partial charges on the bonded atoms

73
Q

What’s a polar molecule?

A

A molecule with an overall dipole, having taken into account any dipoles across bonds, and the shape of the molecule

74
Q

What’s a hydrogen bond?

A

A strong dipole-dipole attraction between an electron deficient hydrogen atom of NH,OH, HF on one molecule, and a lone pair of electrons on a highly electronegative atom (N, O or F) on a different molecule

75
Q

What symbol do you use for a slight charge?

A

Delta δ

76
Q

How do you draw hydrogen bonds?

A

Staggered verticle lines

77
Q

What’s responsible for the higher than expected melting and boiling points of water for a molecule of its size?

A

Hydrogen bonding

78
Q

Why does ice float on water?

A

It’s less dense than water, meaning for a given volume, there are less molecules of H20 in ice than water, this is because when water freezes the molecules are pushed further apart due to the hydrogen bonding

79
Q

How is hydrogen bonding relevant in proteins?

A

Responsible for secondary structure of proteins eg. a-helices, and b-sheets

80
Q

What’s responsible for the double helix structure in DNA?

A

Hydrogen bonding, adenine to thymine, and cytosine to guanine

Chemistry A level (16 decks)

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