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Chemistry > Bonding > Flashcards

Bonding Flashcards

1
Q

define a covalent bond

A

a pair of electrons shared between two atoms to obtain a full outer shell. both nuclei are attracted electrostatically to the shared electrons

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1
Q

why do simple covalent compounds have low melting and boiling points?

A

down to molecules within the compound having weak intermolecular forces

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2
Q

what is the structure of graphite?(3 points)

A

carbon atoms arranged in sheets of flat hexagons covalently bonded with three bonds each. the fourth outer electron of each carbon atom is delocalised. sheets are bonded together by weak van der waals forces

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3
Q

explain why graphite is used in pencils+dry lubricant

A

weak bonds between the layers are easily broken, so sheets can slide over each other making it slippery

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4
Q

why can graphite conduct electricity but diamond cant?

A

delocalised electrons are free to move along the sheets, so electric current can flow

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5
Q

why is graphite insoluble in any solvent and has a high melting point?

A

the covalent bonds in the sheets are too difficult to break

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6
Q

describe the structure of diamond

A

each carbon atom= bonded to four other carbon atoms arranging themselves in a tetrahedral stucture( crystal lattice structure)

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7
Q

give four properties of diamond

A
  • very high melting point
  • diamond extremely hard
  • cant conduct electricity
  • wont dissolve in any solvent
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8
Q

define an ionic bond

A

an electrostatic attraction between positive and negative ions

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9
Q

describe the electrical conductivity of ionic compounds

A

can conduct electricity when molten or dissolved as the ions are free to move, in a solid=fixed position

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10
Q

describe the melting points of ionic compounds

A

high melting points because of the strong electrostatic forces holding the giant ionic lattices together

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11
Q

describe ionic compounds solubility

A

tend to dissolve in water as it is polar, so the water molecules pull the ions away from the lattice so it dissolves

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12
Q

draw ammonia and its charge clouds

A
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13
Q

what is the 2nd biggest bond angle formed between?

A

lone pair/bonding pair

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14
Q

what forms the least biggest bond angle?

A

bonding pair/bonding pair

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15
Q

define electronegativity

A

the ability of an atom to attract bonding electrons in a covalent bond

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16
Q

why are diatomic gases non-polar?

A

atoms have equal electronegativities, so electrons are equally attracted to both nuclei

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17
Q

what is a polar bond?

A

a covalent bond where a difference in electronegativity has caused a shift in electron density in the bond

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18
Q

What are the three intermolecular forces?

A

-induced dipole-dipole(van der walls)
- permanent dipole-dipole forces
- hydrogen bonding

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19
Q

what is van der waals forces also known as?

A

induced dipole-dipole forces

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20
Q

how do van der waals forces come around?

A

every molecules have them as the electrons move around in the charge cloud causing a temporary dipole whereby one atom becomes delta positive the other becomes delta negative. it induces molecules nearby as the S+ on one atom will be attracted to the S- on another molecule

21
Q

what is the strength of van der waals dependent on?

A

size of the molecule, bigger the molecule bigger the van der waals forces as larger electron clouds e.g longer the straightchain hydrocarbon

22
Q

explain why branched hydrocarbons have weaker van der waals then non-branched ones

A

cant pack closely together therefore weakening the van der waals

23
Q

explain why hydrocarbons are non polar

A

carbon and hydrogen have similar electronegativities

24
Q

why are symmetrical molecules non polar?

A

electrons are pushed either side equally

25
Q

what is the molecular formula of a nitrate ion?

A

NO3-

26
Q

what is a metallic bond?

A

electrostatic attraction between a positive metal ion and a sea of delocalised electrons

27
Q

what can the strength of a metallic bond be dependent on?

A

the amount of electrons an atom donates to the sea of delocalized electrons. more electrons stronger the electrostatic attraction between the positive ion and sea of delocalised electrons

28
Q

give four properties of metallic bonds

A

-thermal conductors
- high MP
- electrical conductors
-insoluble

29
Q

what is a dipole?

A

a difference in charge between two atoms caused by a shift in electron density in a bond

30
Q

how can polar molecules be tested?

A

placing a charged rode near a steady stream of polar liquid like water. liquid bends towards the rod as molecules align to face oppositely charged rod

31
Q

how do the hydrogen halides melting points change from HF to HI?

A

HF is highest-hydrogen bonding. then a significant decrease but then slightly increases as the atoms get bigger from Cl to I, increasing the strenght of van der waals

32
Q

what shape of molecule has 2 electron pairs and no lone pairs and 180 degrees bond angle

A

linear

33
Q

how many lone pair and bonding pairs does a linear shape have?

A

LP:0
BP:2

34
Q

what bond angle does a linear shape have?

A

180 degrees

35
Q

draw BeCl2 and what is its shape?

A

linear

36
Q

what shape has no lone pairs and 3 bonding pairs and a bond angle of 120 degrees

A

trigonal planar

37
Q

how many lone pairs and bonding pairs does a trigonal planar shape have?

A

LP: 0
BP: 3

38
Q

what bond angle does a trigonal planar shape have?

A

120 degrees

39
Q

draw BF3 and what is its shape?

A

trigonal planar

40
Q

another type of shape is bent what does this one derive from compared to the original one?

A

trigonal planar

41
Q

bent derived from trigonal planar, how many lone pairs does it have and bond pairs

A

BP:2
LP: 1

42
Q

what shape has got 0 lone pairs and 4 bonding pairs with a bond angle of 109 degrees

A

tetrahedral

43
Q

how many lone pairs and bonding pairs does tetrahedral shape have?

A

LP:0
BP:4

44
Q

what shape has methane have? draw it

A

tetrahedral

45
Q

what shape is trigonal pyramid derived from?

A

tetrahedral

46
Q

how many lone pairs and bonding pairs does a trigonal pyramid shape have? what is its bond angle?

A

LP:1
BP:3
109 degrees

47
Q

what shape does ammonia have and draw it

A

trigonal pyramid

48
Q

what is a charge cloud?

A

region where around the nucleus where you have a 95% chance of finding an electron

49
Q

what is the shape of the molecule dependent on?

A

distrubution of charge clouds around the central atom

Chemistry (23 decks)

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