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chemistry > bonding structure, energy changes, and properties > Flashcards

bonding structure, energy changes, and properties Flashcards

1
Q

melting definition

A

melting requires enough energy to disrupt the bonds between atoms/molecules/ions/metal atoms

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2
Q

metal definition

A

metals are:

  • made up of metal atoms
  • held together in a 3D lattice by metallic bonding
  • this is the strong attraction between the positively charged nuclei of the atoms and the delocalised valence electrons
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3
Q

melting point of metal

A

high

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4
Q

why is melting point of metal high

A

the 3D lattice of metal atoms surrounded by a sea of delocalised valence electrons are strongly attached to the nuclei in the lattice which forms strong metallic bonds therefore a large amount of energy is required to break

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5
Q

electrical conductivity

A

electrical conductivity requires a substance to have mobile charged particles

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6
Q

do metals conduct electricity

A

yes

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7
Q

why do metals conduct electricity

A

the valence electrons are free to move throughout the structure

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8
Q

why are metals malleable/ductile

A

the metallic bonds are non-directional as the electrons are delocalised across the lattice therefore when a force is applied the atoms are free to move without disrupting these bonds meaning the structure can change shape without breaking the lattice

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9
Q

are metals soluble in water

A

no

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10
Q

why are metals insoluble in water

A

there is no attraction between the metal atoms and polar water molecules

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11
Q

ionic bonding definiton

A

ionic substances are made up of ions held together by a 3D lattice by ionic bonding. This is strong attraction of positively charged cations and negatively charged anions

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12
Q

boiling definition

A

boiling requires supplying enough energy to break the bonds between the ions

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13
Q

why do ionic substances not conduct electricity in the solid state

A

in the solid state the ions are rigidly held in a lattice by strong ionic bonds, so cannot move around so cannot conduct electricity.

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14
Q

when can ionic substances conduct electricity

A

when molten (l) and in solution (aq)

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15
Q

why can ionic substances conduct electricity when molten and in solution

A

the ions are able to move freely so can conduct electricity

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16
Q

are ionic substances malleable/ductile

A

no

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17
Q

why are ionic substances not malleable/ductile

A

if a force is applied to an ionic lattice it forces ions with the same charge next to each other which repel and the lattice structure breaks meaning ionic substances are brittle

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18
Q

why are ionic substances soluble in water

A

an ionic solid is soluble because the force of attraction between the ions and water is strong enough to overcome the forces holding the ions together along with the forces holding the water molecules together

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19
Q

how do ionic substances dissolve in water

A

when an ionic substance dissolves in water it separates into its ions, the ions are charged and attracted to the charged ends of the polar water molecule. slightly negative charges on oxygen ends of water molecules attract to positive ion, slightly positive hydrogen ends attract to negative ions. causes ions to be surrounded by water molecules and the lattice breaks down

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20
Q

covalent bonding definition

A

strong attraction between the two positive nuclei and one or more shared pair of electrons

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21
Q

covalent networks defintion

A

covalent network solids are made up of atoms held together in a 3D or 2D lattice by covalent bonding. this is the strong attraction between positive nuclei and shared electrons

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22
Q

covalent network melting point

A

high

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23
Q

why is covalent network melting point high

A

made up of atoms held together in a 3D lattice (or 2D) by strong covalent bonding, these bonds require a large amount of energy to break

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24
Q

which lattice in covalent network conduct electricity

A

2D lattices - graphite and graphene

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25
why do 3D lattice's not conduct electricity (covalent network)
all of the valence electrons for each atom (C or Si) form covalent bonds, therefore there are no delocalised valence electrons free to move
26
why do 2D lattices conduct electricity (covalent network)
in graphite and graphene each carbon is bonded to 3 other carbon atoms, this leaves one delocalised valence electron from each carbon atom, these electrons are free to move
27
draw ionic solubility diagram
refer to notes
28
are covalent networks soluble in water
no
29
why are covalent networks insoluble in water
the interaction between the polar water molecule and the atoms is not strong enough to attract the atoms out of the lattice
30
are covalent networks malleable/ductile
no
31
why are covalent networks not malleable/ductile
if a force is applied the directional strong covalent bonds have to be broken before the atoms can move, resulting in breaking the lattice
32
hardness, diamond vs graphite
all the forces of attraction in the 3D lattice of diamond are strong covalent bonds which makes the structure very rigid and gives the property of hardness. In graphite the forces of attraction between the 2D layers are weak allowing the layers to slide over one another making it soft.
33
covalent molecule definiton
molecular substances are made up of discrete neutral molecules with weak intermolecular forces between the molecules
34
what are the 2 types of forces to consider in covalent molecules
- strong covalent bonds between the atoms in the molecules | - weak intermolecular forces between the molecules
35
melting point in covalent molecules
low
36
why is the melting point low in covalent molecules
because the forces are weak they require a small amount of energy to separate the molecules
37
do covalent molecules conduct electricity
no
38
why do covalent molecules not conduct electricity
molecular substances are made up of discrete neutral molecules, because they are neutral they are unable to conduct electricity
39
do polar molecules dissolve in water
yes
40
what dissolves in water
polar molecules dissolve in water.
41
why are polar molecules soluble in water
because the 𝛿−ve oxygen end of the polar water molecule attracts the 𝛿+ve end of the polar molecule and the 𝛿+ve hydrogen attracts the 𝛿−ve end of the polar molecule allowing them to mix
42
why are non-polar molecules insoluble in water
the 𝛿−ve oxygen and the 𝛿+ve hydrogen ends of the polar water molecule attracts adjacent water molecules, because the non-polar molecule has no 𝛿−ve and 𝛿+ve end it does not attract with the polar water molecules preventing them from mixing
43
do non-polar molecules dissolve in water
no
44
VSEPR, shape 'code'
the shape and angle is controlled by minimising repulsion of the electron areas around the central ..... atom. The electron arrangement that minimises repulsion for .... electron areas is .... which results in an angle of .... Because .... electron areas are bonding and ... non bonding, it results in a .... shape with a bond angle of ....
45
VSEPR, compare and contrast
consider, what is similar & what is different: - total electron areas - bond angles - bonding electron areas - non-bonding electron areas - shape name
46
VSEPR, compare and contrast
consider, what is similar & what is different: - total electron areas - bond angles - bonding electron areas - non-bonding electron areas - shape name
47
compare and contrast the shapes and bond angles of H2O and SO2
refer to notes
48
compare and contrast the shapes and bond angles of H2O and NH3
refer to notes
49
what do polar molecules require
an uneven spread of charge over the molecule
50
how to identify if a molecule is polar
1- there are different terminal atoms 2- there are lone pair(s) (non-bonding electrons) around the central atom OTHERWISE the molecule is NON-POLAR
51
polarity code:
1- define the requirements of molecular polarity 2-describe the polarity of individual bonds using electronegativity 3-link the molecules shape to symmetry and thus the effect on bond dipoles
52
molecular polarity definition
molecular polarity is the distribution of charge about the central ... atom
53
polarity code for CCl4
refer to notes
54
polarity code for H2O
refer to notes
55
polarity code for COCl2
refer to notes
56
solubility
like dissolves like
57
do polar molecules dissolve in cyclohexane
no
58
why do polar molecules not dissolve in cyclohexane
because the 𝛿−ve and 𝛿+ve ends of the polar water molecule are attracted to 𝛿−ve and 𝛿+ve ends respectively of neighbouring polar molecules. The non-polar cyclohexane has no 𝛿−ve and 𝛿+ve ends, meaning they are unable to mix
59
do non-polar molecules dissolve in cyclohexane
yes
60
why do non-polar molecules dissolve in cyclohexane
because the non-polar molecule has no 𝛿−ve and 𝛿+ve end the two substances have similar intermolecular forces which allows them to mix

chemistry (3 decks)

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