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AQA Alevel Chemistry > Bonding > Flashcards

Bonding Flashcards

1
Q

Define ionic bonding

A

Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice

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2
Q

What is the compound formula for sulfate?

A

SO4^2-

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3
Q

What is the compound formula for sulfate?

A

SO4^2-

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4
Q

What is the formula for hydroxide ?

A

OH-

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5
Q

What is the formula for carbonate ?

A

CO3^2-

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6
Q

What is the formula for ammonium?

A

NH+4

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7
Q

Define covalent bonding

A

A single covalent bond contains a shared pair of electrons
Held by electrostatic attraction

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8
Q

What do multiple bonds contain ?

A

Multiple bonds contain multiple pairs of electrons

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9
Q

Define a coordinate /dative covalent bond

A

Contains a shared pair of electrons with both electrons supplied by one atom

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10
Q

What happens in a coordinate covalent bond ?

A

-atom accepts the electron pair is an atom that doesn’t have a filled outer main level of electrons-atom is electron deficient
-the atom is donating the electrons has a pair of electrons that is not being used in a bond called a lone pair

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11
Q

What are the similarities with an ordinary covalent bond and coordinate bonds?

A

Coordinate bonds have exactly the same strength and length as ordinary covalent bonds between the same pair of atoms

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12
Q

Define metallic bonding

A

Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice

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13
Q

What does the number of delocalised electrons depend on ?

A

Number of delocalised electrons depends on how many electrons have been lost by each metal atom

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14
Q

What are the properties of metals?

A

Good conductors of electricity
Good conductors of heat
Malleable
Ductile
High mpg and bpt

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15
Q

Why are metals good conductors of electricity?

A

Delocalised electrons move freely throughout the structure enabling current to flow

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16
Q

Why are metals good conductors of heat?

A

Closely packed ions enables efficient spread of energy through vibrations

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17
Q

Why are metals malleable and ductile ?

A

Layers of positive ions can slide over each other

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18
Q

Why do metals have high mpt and bpt?

A

Strong electrostatic attraction between positive ions and delocalised electrons

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19
Q

Define electronegativity

A

Electronegativity is the power of an atom to draw electron density in a covalent bond towards itself

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20
Q

What scale shows how electronegative an atom is?

A

Pauling scale=0-4 the greater the number the more electronegativite the atom the noble gases have no number because they do not in general form covalent bonds

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21
Q

What does electronegativity depend on?

A

Nuclear charge
Distance between the nucleus and the outer shell electrons
Shielding of nuclear charge by electrons in inner shell

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22
Q

Describe nuclear charge in electronegativity terms

A

Attraction between positive protons in the nucleus and electrons .an increase in protons means increased attraction for electron number in outer shells thus increased nuclear charge means increased electronegativity

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23
Q

Describe atomic radii in terms of electronegativity

A

Electrons closer to nucleus are more strongly attracted to positive nucleus electrons further away are less attracted so higher atomic radii means decreased electronegativity

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24
Q

Describe shielding of nuclear charge by electrons in inner shells through electronegativity

A

Filled energy levels can shield the effects of nuclear charge outer electrons are less attracted to nucleus thus adding extra shells/sub shells in atom will cause electrons to feel less attractive force higher number of inner shells and sub shells decreases electronegativity

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25
What does a smaller atom mean in terms of electronegativity?
Smaller atom =closer nucleus is to shared outer main level electrons -greater electronegativity
26
What happens to electronegativity down a group?
-decrease in electronegativity down the group -nuclear charge increases (more protons added to nucleus) -however each element has an extra filled electron shell increasing shielding -addition of extra shell increase distance between nucleus and outer shell electrons =larger atomic radii
27
What happens to electronegativity down a group?
-decrease in electronegativity down the group -nuclear charge increases (more protons added to nucleus) -however each element has an extra filled electron shell increasing shielding -addition of extra shell increase distance between nucleus and outer shell electrons =larger atomic radii
28
What happens to electronegativity across a period?
-electronegativity increased - nuclear charge increase with addition of protons -shielding remains constant as no new shells added to atoms - nucleus has increasingly strong attraction for bonding pair of electrons the period of the per table
29
Why don’t noble gases share electrons?
Noble gases don’t share electrons full outer shell doesn’t form bonds
30
What molecule is a molecule if it contains polar bonds but it’s symmetrical?
If a molecule contains polar bonds but it’s symmetrical it’s a nonpolar molecule. This is due to the dipole which are directional and will council out if they are equal and the opposite directions.
31
What makes intermolecular forces different from covalent and ionic?
Intermolecular forces are weaker than covalent and ionic bonds
32
What are the three types of intermolecular forces?
Van der waals – act between all atoms and molecules (even noble gases) Dipole – dipole – act only between certain molecule types (changes properties) Hydrogen bonding – act only between certain molecule types
33
What is the relative strength of ionic and covalent bond hydrogen bond dipole – dipole forces and van der waal forces?
Ionic &covalent=1000 Hydrogen=50 Dipole-dipole forces=10 Van der waals forces=1
34
Describe van der waals between atoms
Roughly vertical atoms of an ideal gas shouldn’t be attracted or repelled by one another (if this were really the case, the noble gases couldn’t be liquified In a real gas atom, electrons are constantly moving and any one time it can have an instantaneous dipole due to an uneven distribution of these electrons This atom can vent induced dipole in a neighbour molecule. There’s then an attraction between these molecules – there’s a temporary induced dipole – dipole attraction.
35
Describe VanderWaal forces between molecules
The electron density is spread equally throughout the molecule At any given time it’s possible for the electron density to be anywhere in this case the electron density is located mainly on the right generating a temporary dipole which has a fleeting existence If two hydrogen molecules are separated by a large distance dipole can’t be induced. If two hydrogen molecules are in close proximity and temporary dipole can be induced.
36
What is the boiling point of noble gases increased down the group?
Noble gases have a larger number of electrons larger electron density, larger dipole so the boiling point of noble gases increases down the group
37
Describe a polar bond
Polar bond is a covalent bond in which the bpt of electrons are unequally shared and there’s a separation of charge between end and the other eg HCL It occurs because of a significant difference in electronegativity between the two atoms of the covalent bonds
38
Describe van der waals
Present in all molecular substances Electrons are constantly moving around and there will be an uneven electron distribution at any given moment in time Causing a temporary dipole within a molecule This temporary dipole induces a temporary dipole in a neighbouring molecule There’s then an attraction between molecules -temporary induced dipole dipole attraction The larger the molecule I e more electrons the larger the induced dipole the greater the van der waals forces so the higher the boiling point Van der waals forces are the only attractions between non polar molecules
39
Non polar molecules
Molecules that don’t have any electrical charges or partial charges
40
What are dipole dipole attractions only between
Only between polar molecules -some molecules are non polar but contain polar bonds these don’t have permanent dipole dipole attraction
41
Why do polar bonds occur?
Polar bonds occur because of a significant difference in electronegativity between the two atoms of the covalent bonds
42
Describe the hydrogen bond
Dipole dipole attractions - some of a covalent bond Consists of a hydrogen atom between two very electronegative atoms
43
What are the conditions for hydrogen bonding
Very electronegative atom with lone pair of electrons covalently bonded to a hydrogen atom (Water molecular fulfill these conditions- oxygen is more electronegative than hydrogen so water is polar
44
Why is the intermolecular bonding of hydrogen atoms strong?
Would expect weak dipole dipole attraction but there aren’t because Oxygen atoms in water have lone pairs of electrons In water the hydrogen atoms are highly electron deficient (why?- Oxygen is very electronegative and attracts shared electrons in the bond towards it Hydrogen atoms in water are positively charged and very small exposed protons have a very strong electric field due to their small size
45
Where is the lone pair in a water molecule and what is it attracted to ?
The lone pair of electrons on the oxygen atom of another water molecule is strongly attracted to the electron deficient hydrogen atom the strong intermolecular force is called a hydrogen bind
46
In terms of structure, what are hydrogen bonds?
Always linear the pair of electrons in the covalent bond repels those in the hydrogen bond
47
How strong are hydrogen bonds?
Stronger than dipole – dipole Weaker than covalent
48
Which atoms can form hydrogen bonds?
Only atoms electronegative enough to form hydrogen bonds are oxygen nitrogen and fluorine
49
What must happen to form a hydrogen bond?
Hydrogen is that bonded to a very electronegative atom (will produce a strong partial positive charge on the hydrogen atom) Very electronegative atom with a lone pair of electrons will be attracted to partially charged hydrogen atoms in the molecule and form the bond
50
Describe the boiling points of hydrides
Noble gases – gradual increase in boiling points due to the early forces acting between the atoms being van der waals forces – increase the number of electrons present Water, hydrogen fluoride ammonia -higher than those of the hydrides of the other elements in the group due to the hydrogen bonding being present between the molecules in each of those compounds and these stronger intermolecular forces of attraction make the molecules more difficult to separate
51
Why are hydrogen bond significant?
Hydrogen bonds are weaker than covalent bonds and can make or break under conditions where bonds are unaffected– makes them very significant
52
Describe the structure and bonding in ice
In water, the liquid state of ice hydrogen bonds break and reform easily as molecules are moving about When water freezes water molecules are no longer free to move out and hydrogen bonds molecules in fixed position
53
Why is ice less dense than water ?.
Molecules are slightly less closely packed in liquid water – means ice is less than water and forms on top of pond rather than at the bottom this insulates the ponds and enables fish to survive through the winter helps to continue in the relative warmth of water under ice
54
Describe the electron pair repulsion theory
Each pet of electrons around an atom will repel all other electron pairs Pairs of electrons will thus take up positions as far apart as possible to minimise repulsion
55
What does a shape of a single molecule depend on ?
Shape of molecule depends on the number of pairs of electrons that surround the central atom to work out the shape of any molecule first draw a dot and cross diagram to find the number of pair of electrons
56
Describe what the molecule would be if it has two pairs of electrons
Molecule will be linear Furthest away from each other, the two can get is 180 degrees apart
57
Describe what the molecule would be if they had three pairs of electrons
120° apart Trigonal planar Three pairs central atom
58
Describe what’s the molecule would be if it had four pairs of electrons
Furthest apart when arranged Tetrahedral 109.5° Three dimensional, so some of angles can be more than 360° Ion has an overall charge that doesn’t affect shape
59
Describe what molecule would be if it had five pairs of electrons
Trigonal by pyramid 120°
60
Describe a molecule would be had six pairs of electrons
Octahedral 90°
61
Describe molecules with lone pairs electrons
Not a part of covalent bonds Lone pairs affect the shape of molecules, for example, ammonia and water as well offering
62
Describe ammonia in terms of its lone pair
Four pairs of electrons and one of the groups is alone pair Shape based on a tetrahedron Only three arms so shape is a triangular pyramid
63
Describe lone pair repulsion
Repulsion between lair and electrons and abundant pair electrons is greater than that between two bonding pairs Approx rule of thumb is 2.5 per lone pair
64
How does repulsion increase ?
Bonding pair bonding pair Lone pair bonding pair Lone pair lone pair

AQA Alevel Chemistry (23 decks)

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