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chemistry > bonding > Flashcards

bonding Flashcards

1
Q

what is an ionic bond

A

an ionic bond is the electrostatic forces of attraction between oppositely charged ions

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2
Q

what is a covalent bond

A

a covalent bond is the electrostatic forces of attraction between a shared pair of electrons and both the nuclei of the two atoms

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3
Q

what is a metallic bond

A

a metallic bond is the electrostatic force of attraction between the positive metal ions and the sea of delocalised electrons

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4
Q

what is electronegativity

A

electronegativity is the ability of an atom to attract a pair of electrons in a covalent bond

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5
Q

what kind of electronegativities in an ionic bond

A

when there is a big difference of electronegativity the electrons are transferred from the element of low electronegativity and the bonding is ionic

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6
Q

what kind of electronegativity in a covalent bond

A

when both atoms have a medium to high electronegativity and there is a small difference the electron pair is shared evenly between the two elements and the bonding is covalent

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7
Q

what kind of electronegativity in metallic bonds

A

when both atoms have low electronegativity and there is only a small difference they tend to form metallic bonds

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8
Q

what are polarised ions

A

electron clouds in ions become distorted and lop sided resulting in partial sharing of electrons

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9
Q

what are polar molecules

A

one end of the molecule is slightly more negative than the other

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10
Q

generally metals have … electronegativity values and so only hold on … to their outer shell electrons

A

low
weakly

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11
Q

generally non metals have … electronegativity and so hold on … to their outer shell electrons

A

high
strongly

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12
Q

metal atoms … electrons to form … ions
non metal atoms … electrons to form … ions

A

lose
positive
gain
negative

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13
Q

explain ionic compounds mpt and bpt

A

ionic bonds are very strong and it takes a lot of energy to overcome them. this means that ionic compounds are solids at room temp and have high mpt and bpt

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14
Q

the strength of ionic bonds increases as
the charge on ions …
the size of ions …

A

increases
decreases

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15
Q

explain whether ionic compounds conduct electricity

A

ionic compounds don’t conduct electricity when they are in the solid state however they do when molten or dissolved in water because ions are free to move

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16
Q

explain solubility of ionic compounds

A

ionic compounds are generally soluble in polar solvents like water and insoluble in non polar solvents like cyclohexene

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17
Q

explain hardness in ionic compounds

A

Ionic compounds are relatively hard due to the strength of the bonds between oppositely charges ions therefore a lot of force is required to overcome these bonds

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18
Q

explain brittleness in ionic compounds

A

ionic compounds are brittle and break when a large enough force is applied in a specific direction. this is caused by laters of ions slipping over each other and the ions of same charge come into contact repelling and break the structure

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19
Q

electron pairs that form bonds are called … pairs. electron pairs that are not involved in bonding are called … pairs

A

bonding
lone

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20
Q

which bond is stronger a C-H or a Si-H bond and why

A

C-H because C is smaller atom than Is and so the shared electrons are closer to the nucleus of carbon and so are attracted more strongly than Si

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21
Q

what is the general rule about atom size and bond strength

A

the smaller the atom the shorter the bond length and the stronger the bond

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22
Q

what is a dative or coordinate bond

A

both bonding electrons come from the same atom in the molecule
once it has formed it behaves the same way as an ordinary covalent bond
a coordinate bond is shown with an arrow

23
Q

the basic shape of a molecule or compound ion is determined by the number of … electrons around the central atom. these pairs of electrons … each other as far away as possible and this mutual … determines molecular shape

A

pair
repulse
repulsion

24
Q

basic shape of molecule may be distorted by the presence of ….
why are they distorted

A

lone pairs
closer to the nucleus than bonding pairs so they repel more strongly

25
Q

basic shapes of two pairs of electrons

A

linear
180°

26
Q

basic shape of three pairs of electrons

A

trigonal planar
120°

27
Q

basic shape of four pairs of electrons

A

tetrahedral
109.5°

28
Q

basic shape of five pairs of electrons

A

trigonal bipyramidal
90° axial position
120° equatorial position

29
Q

basic shape of six pairs of electrons

A

octahedral
90°

30
Q

how much does a lone pair reduce a bond angle

A

by 2.5°

31
Q

basic shape 2 bonding 1 lone pair

A

117.5°
bent or v shaped

32
Q

basic shape 3 bonding 1 lone pair

A

107°
pyramidal

33
Q

basic shape 2 bonding 2 lone pair

A

104.5°
bent or v shaped

34
Q

basic shape 4 bonding 1 lone pair

A

see saw shaped
87.5° - axial
117.5° - equatorial

35
Q

basic shape 3 bonding 2 lone pair

A

t shaped
85°

36
Q

basic shape 2 bonding 3 lone pair

A

linear
180°

37
Q

basic shape 5 bonding 1 lone pair

A

square based pyramid

38
Q

basic shape 4 bonding 2 lone pair

A

square planar
not affecting bond angles because they re in opposite positions and so their effects cancel each other out

39
Q

explain why SiH4 is tetrahedral

A

outer shell of silicon there are four bonding pairs of electrons only. these electron pairs repel each other equally and the molecule adopts the shape hat minimises the repulsive forces

40
Q

the further… and … you go in the periodic table the more electronegative the element is

A

up
right

41
Q

what is the most electronegative element

A

fluorine

42
Q

what can help quantify electronegativity of element

A

pauling scale

43
Q

covalent bonds can become polar if the atoms attached to it have a …

A

difference in electronegativity

44
Q

… of charge leads to polar molecules

A

uneven distribution

45
Q

what are van der waals

A

induced dipole dipole forces that exist between atoms and molecules

46
Q

rank the intermolecular forces by strength

A

hydrogen bonding
permanent dipole
van der waals- weakest

47
Q

how does a dipole form

A

when electrons in a molecule or atom move from one end to another

48
Q

how does size of particle affect van Der waals

A

the bigger the molecule or atom, the more van der waals forces as you have larger electron clouds

49
Q

branched vs non branched hydrocarbon bpt

A

longer straight chain hydrocarbons have more van der waals and so more energy needed so higher bpt, branched hydrocarbons means that they can’t pack together as close weakening van der waals and lowering bpt

50
Q

what are dipole dipole forces

A

weak electrostatic forces that exist between molecules with a polarity

51
Q

what is hydrogen bonding

A

strongest intermolecular force and occurs when you have very electronegative elements

52
Q

when does hydrogen bonding occur

A

hydrogen bonding occurs when hydrogen on one molecule forms a bond with the lone pair of nitrogen oxygen or fluorine

53
Q

why is ice less dense than liquid water

A

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

54
Q

how is metal thermal conductivity

A

very good as delocalised electrons can transfer kinetic energy

chemistry (15 decks)

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