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chemistry > bonding (physical) > Flashcards

bonding (physical) Flashcards

1
Q

what is ionic bonding

A

strong electrostatic force between oppositely charged ions

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2
Q

give an example of an ionically bonded substance

A

sodium chloride (NaCl)

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3
Q

how high are ionically bonded substances’ boiling and melting points? why?

A

very high because it takes a lot of energy to break electrostatic forces between oppositely charged ions

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4
Q

do ionic compounds conduct electricity? why?

A

yes when molten/dissolved in a solution because they are free to move around and hold a charge. they do not conduct electricity when solid

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5
Q

what is simple molecular covalent bonding?

A

strong covalent bonds between atoms, weak van der waals forces between molecules

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6
Q

are there any lone electrons in simple covalent bonding

A

no

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7
Q

can simple covalent bonds conduct electricity? why?

A

no because all of the electrons are used in bonding and arent free to move

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8
Q

do simple molecular covalent substances have high or low boiling and melting points? why?

A

low because there are weak van de Waals forces that dont need much energy to overcome

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9
Q

describe macromolecular covalent bonding

A

lattice of many atoms held together by strong covalent bonds

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10
Q

do substances with macromolecular covalent bonds have high or low melting and boiling points? why?

A

high because it takes a lot of energy to overcome lots of covalent bonds

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11
Q

do substances with macromolecular covalent bonds conduct electricity? why?

A

most of them dont as electrons are all used in bonding
graphite does as there is a delocalised electron from each carbon free to carry charge

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12
Q

describe the structure of diamond

A

tetrahedral 3D structure of carbon atoms, each bonded to 4 other carbon atoms

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13
Q

describe the structure of graphite

A

each carbon atom is bonded to 3 other carbons so it is in layers.
there are weak van de waals forces in between layers so that they can easily slide over eachother.
one electron from each carbon is delocalised so can conduct electricity

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14
Q

describe metallic bonding

A

lattice of positive metal ions attracted to a sea of delocalised electrons
layers can also slide over eachother meaning they are malleable

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15
Q

do metallic compounds have low or high melting and boiling points? why?

A

high because there are strong forces of attraction between metal ions and negatively charged sea of delocalised electrons

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16
Q

do metallic compounds conduct electricity? why?

A

yes because there are delocalised electrons free to carry charge

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17
Q

how does the strength of metallic bonds change across the periodic table? why?

A

strength increases - higher melting and boiling points
higher charge on metal ions
more delocalised electrons per ion
stronger force of attraction between them

18
Q

define electronegativity

A

the ability of an atom to attract the pair of electrons (the electron density) in a covalent bond

19
Q

what affects electronegativity? (3)

A

nuclear charge
atomic radius
electon shielding

20
Q

what is the most electronegative element?

A

fluorine (4.0 on paulings scale) largest nuclear charge for its electron shielding and a small atomic radius

21
Q

how do you get a non-polar bond?

A

both bonding elements have the same electronegativities

22
Q

when do you get a polar bond?

A

when both elements have different electronegativities

23
Q

what is the strongest type of intermolecular force

A

hydrogen bonding

24
Q

what is the weakest type of intermolecular force?

A

van der Waals forces

25
Q

describe Van der Waals forces

A

temporary dipoles are created by random movement of electrons -> induces dipole in neighbouring molecule

26
Q

are van der Waals forces stronger in smaller or larger molecules

A

larger because there are more electrons

27
Q

describe permanent dipole-dipole attraction

A

some molecules with polar bonds have permanent dipoles (forces of attraction between those dipoles and those of neighbouring molecules)

28
Q

what conditions are needed for hydrogen bonding to occur

A

O-H, N-H or F-H bond
lone pair of electrons on O,N,F because they are highly electronegative so H nucleus is left exposed
strong forces of attraction between H nucleus and lone pair of electrons on O, N,F

29
Q

why is ice less dense than liquid water

A

in liquid water, hydrogen bonds constantly break and reform as molecules move around
in ice, the hydrogen bonds hold the molecules in fixed positions which makes them slightly further apart than liquid water

30
Q

what is a dative/co-ordinate covalent bond? when is it formed?

A

formed when an electron deficient atom/ion accepts a lone pair of electrons from an atom with a lone pair of electrons not used in bonding

31
Q

what does the shapes of molecules depend on?

A

number of electrons in the valence shell of the central atom
number of these electrons that are bonded or lone pairs

32
Q

what does the electron pair repulsion theory state?

A

the electron pairs will take up positions as far away as possible to minimise the repulsive forces between them

33
Q

which experience the most repulsion?
lone pair-lone pair
bonded pair-bonded pair
lone pair-bonded pair

A

lone pair - lone pair (strongest)
lone pair - bonded pair
bonded pair - bonded pair (weakest)

34
Q

what is the shape, and angle in a shape with 2 bonded pairs and 0 lone pairs

A

linear , 180°

35
Q

what is the shape and angle of a shape with 3 bonded pairs and 0 lone pairs

A

trigonal planar , 120°

36
Q

what is the shape and angle of a shape with 4 bonded pairs and 0 lone pairs

A

tetrahedral , 109.5°

37
Q

what is the shape and angle of a shape with 5 bonded pairs and 0 lone pairs

A

trigonal bipyramid
90° and 120°

38
Q

what is the shape and angle of a shape with 6 bonded pairs and 0 lone pairs

A

octahedral
90°

39
Q

what is the shape and angle of a shape with 3 bonded pairs and 1 lone pair

A

trigonal pyramidal, 107°

40
Q

what is the shape and angle of a shape with 2 bonded pairs and 2 lone pairs

A

non linear, 104.5°

41
Q

how are ionic compounds soluble in polar substances such as water

A

the polar solution surrounds the ions and can overcome the electrostatic forces of attraction

42
Q

how do lone pairs effect repulsion

A

decrease the angle by 2.5°

chemistry (34 decks)

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