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Dr stead chem > Bonding > Flashcards

Bonding Flashcards

1
Q

What is ionic bonding?

A

the force of attraction between oppositely charged ions

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2
Q

How are the ions formed in ionic bonding?

A

the ions are formed by the transfer of electrons from metal atoms to non-metal atoms

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3
Q

What layer of electrons are involved in ionic bonding?

A

only the outer electrons

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4
Q

What happens to metal atoms in ionic bonding?

A

they lose electrons to form cations (+)

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5
Q

What happens to non-metal atoms in ionic bonding?

A

they gain electrons to form anions (-)

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6
Q

What state are ionic compounds in when at room temperature?

A

solids with high melting and boiling points

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7
Q

What does the strength of the attractive forces depend on in ionic bonding?

A

the size and charge of the ions

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8
Q

The electrostatic forces increase in strength as…

A

-the charge on the ion increases
-the size of the ion decreases

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9
Q

What is a crystal?

A

a solid with a regular shape which contains particles organised in a regular structure

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10
Q

How are the ions arranged in a giant ionic lattice?

A

in a regular repeating pattern

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11
Q

What type of diagram should you draw in an exam to represent an ionic compound?

A

a ball and stick diagram

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12
Q

What other diagram can you draw to represent ionic compounds?

A

space filling

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13
Q

What are the advantages of space filling diagrams?

A

they are 3D models
they accurately show the space taken up by each ion

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14
Q

What are the disadvantages of space filling diagrams?

A

difficult to see the the structure of the whole ionic lattice clearly
bonds are not shown clearly

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15
Q

What are the advantages of ball and stick diagrams?

A

they are 3D models
they allow you to see the structure of the whole ionic lattice clearly as bonds are shown as lines

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16
Q

What is the limitation of ball and stick diagrams?

A

not actually representative of the space taken up by the ions

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17
Q

Why do ionic crystals have high melting points?

A

because they contain a very large number of strong ionic bonds which require a lot of energy to break

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18
Q

What are ionic crystals like?

A

hard and brittle

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19
Q

What are ionic crystals usually soluble in?

A

water

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20
Q

Why do ionic crystals not conduct electricity?

A

because the ions are not free to move and carry a current

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21
Q

When can ionic compounds conduct electricity and why?

A

when an ionic compound is melted or in solution it can conduct electricity because the ions are free to move and carry the current

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22
Q

Why are ionic compounds always neutrally charged?

A

the charges on the positive and negative ions balance out

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23
Q

What is the coordination number?

A

the number of ions that one particular ion in a lattice is in contact with

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24
Q

Why are ionic compounds soluble in water?

A

in solution an ionic compound will fully ionise and so positive and negative ions can fit between water molecules arranged such that oppositely charged regions interact

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25
Q

Describe in detail the structure and bonding in a sodium chloride crystal

A

bonding-
1 sodium atom transfers 1 electron to 1 atom of chlorine
this results in the formation of a Na+ ion and a Cl- ion
the oppositely charged ions are attracted to one another by strong ionic bonds
these strong electrostatic forces require a lot of energy to break

structure-
there is a strong electrostatic attraction between the Cl- and the Na+ ions, and they are arranged in a giant ionic lattice
each ion is by 6 other oppositely charged ions
the crystal is cubic and has a coordination number of 6

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26
Q

What is a covalent bond?

A

a single shared pair of electrons

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27
Q

What is covalent bonding between?

A

two non metals

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28
Q

What is a lone pair of electrons?

A

non-bonded pairs of electrons in a compound

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29
Q

What is a co-ordinate/dative bond?

A

co-ordinate/dative bonds are formed when one atom contributes both of the electrons needed for the covalent bond from a lone pair on the donor atom

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30
Q

What is octet expansion?

A

when atoms have more than 8 electrons in it’s outer shell

31
Q

How are co-ordinate bonds represented?

A

an arrow

32
Q

What are the two types of covalent structure?

A

simple molecular
giant macromolecular

33
Q

What are some examples of simple molecular structures?

A

water/ammonia/iodine/oxygen

34
Q

What are some examples of giant macromolecular structures?

A

diamond/graphite/silicon dioxide/silicon

35
Q

What do simple molecular structures consist of?

A

small molecules

36
Q

The covalent bonds within the molecules are strong, but…

A

the forces of attraction between the molecules are weak

37
Q

Why do simple molecular compounds have low melting and boiling points?

A

the amount of energy required to break the weak intermolecular forces is small

38
Q

What state are simple molecules in at room temperature?

A

gases or volatile liquids

39
Q

Why are simple molecules non-conductors?

A

no ions or free electrons present in simple covalent compounds

40
Q

What is the structure of solid iodine like?

A

the I2 molecules are held together by van der Waals forces between the adjacent molecules
the distance between the iodine atoms within a molecule is less than the distance between iodine atoms in adjacent molecules
in an iodine crystal the molecules are arranged in a regular repeating pattern

41
Q

Why does iodine have a low melting/boiling point?

A

because the weak van der Waals forces require little energy to break

42
Q

What are allotropes?

A

different forms of the same element in the same physical state

43
Q

What is the bonding in diamond?

A

each carbon atom is covalently bonded to 4 other carbon atoms in a giant covalent structure
the co-ordination number of the carbon atoms is 4
the arrangement of bonds is tetrahedral

44
Q

Why is the melting/boiling point of diamond so high? (3500C)

A

a very large amount of energy is needed to break the large number of strong covalent bonds

45
Q

Why is diamond a non-conductor of electricity?

A

because all of the outer electrons in carbon atoms are involved in bonding so there are no free electrons to carry a current

46
Q

What is the bonding and structure in graphite?

A

each carbon atom is covalently bonded to three other carbon atoms
the co-ordination number of the carbon atoms is 3
the arrangement is trigonal planar

the trigonal planar arrangement leads to the formation of layers in which the carbons form regular hexagons

47
Q

What is the bond angle of diamond?

A

109.5

48
Q

What is the bond angle of graphite?

A

120

49
Q

Why can graphite conduct electricity?

A

each carbon atom in graphite forms three covalent bonds, leaving 1 delocalised free electron between the plates of covalently bonded carbon atoms
the electrons are free to move BETWEEN LAYERS NOT UP AND DOWN

50
Q

Why is graphite soft?

A

it has weak van der Waals forced between the adjacent layers that means they can easily slide over each other

51
Q

Why does graphite have high melting/boiling points?

A

lots of energy is needed to break the large number of strong covalent bonds

52
Q

What is metallic bonding?

A

metallic bonding is the force of attraction between the delocalised electrons and the positive metal ions in a lattice

53
Q

What is the giant metallic lattice?

A

closely packed positive metal ions surrounded by a sea of delocalised electrons

54
Q

Why are do metallic ions have a high melting/boiling point?

A

due to the strong metallic bonds between ions

55
Q

A large amount of energy is needed to…

A

remove a metal atom from the attraction of the delocalised electrons

56
Q

The strength of metallic bonding depends on…

A

the size and charge of the positive ions/the number of mobile electrons per atom

57
Q

Metallic bonding strength increases as…

A

charge on the positive metal ion increases
the size of the metal atom decreases
the number of delocalised electrons per atom increases

58
Q

The electrical conductivity of a metal increases as…

A

the number of delocalised electrons per atom increases

59
Q

What are delocalised electrons also responsible for? (nothing to do with the electrical conductivity)

A

for the metals ability to reflect light

60
Q

Why are metals malleable and ductile?

A

the planes of ions can slide over each other

61
Q

What are metallic crystals usually made from?

A

repeating units which tend to be hexagonal or cubric

62
Q

What is magnesium’s crystal structure?

A

a close-packed hexagonal structure, coordination number of 12

63
Q

What is electronegativity?

A

an atom’s ability to withdraw electron density from a covalent bond

64
Q

Across a period electronegativity…

A

increases because-
atomic radius decreases
the positive nuclear charge increases with similar shielding

65
Q

Down a group electronegativity…

A

decreases because-
increase in atomic radius
more shielding

66
Q

Which elements are the most electronegative and their values?

A

N-3.0/O-3.5/F-4.0

67
Q

In terms of electronegativity, diatomic molecules are always…

A

non-polar as the atoms have the same electronegativity value

68
Q

The greater the difference of the electronegativity value, the more…

A

polarised the bond is

69
Q

Why are some covalent bonds polar?

A

when atoms of different electronegativity are bonded together the more electronegative atom withdraws the electron pair more strongly so has a greater share of the electrons, making it polar

70
Q

Why are some molecules (like CCL4/CO2) non-polar even though they contain polar bonds?

A

these molecules are spherical and therefore the polar bonds within them cancel each other out leaving the molecule non-polar as the electron cloud is symmetrical

71
Q

What is the Pauling scale?

A

a relative measure of how well an atom can attract electrons

72
Q

Why do group 0 not have electronegativity values?

A

they do not form covalent bonds

73
Q

When atoms with SIMILAR electronegativity are bonded together what occurs?

A

covalent bonding and covalent substances are formed

74
Q

When atoms with A LARGE DIFFERENCE in electronegativity are bonded together, what occurs?

A

ionic bonding and ionic substances are formed

Dr stead chem (21 decks)

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