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AQA Alevel Chemistry > Bonding > Flashcards

Bonding Flashcards

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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
Q

What does a smaller atom mean in terms of electronegativity?

A

Smaller atom =closer nucleus is to shared outer main level electrons -greater electronegativity

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26
Q

What happens to electronegativity down a group?

A

-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

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27
Q

What happens to electronegativity down a group?

A

-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

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28
Q

What happens to electronegativity across a period?

A

-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
Q

Why don’t noble gases share electrons?

A

Noble gases don’t share electrons full outer shell doesn’t form bonds

30
Q

What bond is it if both atoms have electronegativities less than 1.6 to 1.9?

A

If both atoms have electronegativities less than 1.6 1.9 then the bond is metallic

31
Q

What wonders it is if eva atom has an electronegativity greater than 1.9 and the difference is less than 0.5

A

If eva atom has an electronegativity greater than 1.9 and the difference is less than 0.5 the bond is covalent

32
Q

What wonders it is if either atom has an electronegativity greater than 1.9 and the difference is more than 0.5 but less than 2.1

A

If either atom has an electronegativity greater than 1.9 and the difference is more than 0.5 but less than 2.1 the bond is polar covalent

33
Q

What one is it if the difference is greater than 2.1?

A

If the difference is greater than 2.1 the bond is ionic

34
Q

What molecule is a molecule if it contains polar bonds but it’s symmetrical?

A

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.

35
Q

What makes into molecular forces different from covalent and ionic?

A

Intermolecular forces are weaker than covalent and ionic bonds

36
Q

What are the three types of intermolecular forces?

A

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

37
Q

What is the relative strength of ionic and covalent bond hydrogen bond dipole – dipole forces and van der waal forces?

A

Ionic &covalent=1000
Hydrogen=50
Dipole-dipole forces=10
Van der waals forces=1

38
Q

Describe van der waals between atoms

A

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.

39
Q

Describe VanderWaal forces between molecules

A

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.

40
Q

What is the boiling point of noble gases increased down the group?

A

Noble gases have a larger number of electrons larger electron density, larger dipole so the boiling point of noble gases increases down the group

41
Q

Describe a polar bond

A

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

42
Q

Describe van der waals

A

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

43
Q

Non polar molecules

A

Molecules that don’t have any electrical charges or partial charges

44
Q

What are dipole dipole attractions only between

A

Only between polar molecules -some molecules are non polar but contain polar bonds these don’t have permanent dipole dipole attraction

45
Q

Why do polar bonds occur?

A

Polar bonds occur because of a significant difference in electronegativity between the two atoms of the covalent bonds

46
Q

Describe the hydrogen bond

A

Dipole dipole attractions - some of a covalent bond
Consists of a hydrogen atom between two very electronegative atoms

47
Q

What are the conditions for hydrogen bonding

A

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

48
Q

Why is the intermolecular bonding of hydrogen atoms strong?

A

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

49
Q

Where is the lone pair in a water molecule and what is it attracted to ?

A

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

50
Q

In terms of structure, what are hydrogen bonds?

A

Always linear the pair of electrons in the covalent bond repels those in the hydrogen bond

51
Q

How strong are hydrogen bonds?

A

Stronger than dipole – dipole
Weaker than covalent

52
Q

Which atoms can form hydrogen bonds?

A

Only atoms electronegative enough to form hydrogen bonds are oxygen nitrogen and fluorine

53
Q

What must happen to form a hydrogen bond?

A

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

54
Q

Describe the boiling points of hydrides

A

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

55
Q

Why are hydrogen bond significant?

A

Hydrogen bonds are weaker than covalent bonds and can make or break under conditions where bonds are unaffected– makes them very significant

56
Q

Describe the structure and bonding in ice

A

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

57
Q

Why is ice less dense than water ?.

A

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

58
Q

Describe the electron pair repulsion theory

A

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

59
Q

What does a shape of a single molecule depend on ?

A

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

60
Q

Describe what the molecule would be if it has two pairs of electrons

A

Molecule will be linear
Furthest away from each other, the two can get is 180 degrees apart

61
Q

Describe what the molecule would be if they had three pairs of electrons

A

120° apart
Trigonal planar
Three pairs central atom

62
Q

Describe what’s the molecule would be if it had four pairs of electrons

A

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

63
Q

Describe what molecule would be if it had five pairs of electrons

A

Trigonal by pyramid
120°

64
Q

Describe a molecule would be had six pairs of electrons

A

Octahedral
90°

65
Q

Describe molecules with lone pairs electrons

A

Not a part of covalent bonds
Lone pairs affect the shape of molecules, for example, ammonia and water as well offering

66
Q

Describe ammonia in terms of its lone pair

A

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

67
Q

Describe lone pair repulsion

A

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

68
Q

How does repulsion increase ?

A

Bonding pair bonding pair
Lone pair bonding pair
Lone pair lone pair

AQA Alevel Chemistry (8 decks)

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