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A Level Chemistry- KE > Bonding > Flashcards

Bonding Flashcards

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1
Q

what is ionic bonding?

A

strong electrostatic attraction between oppositely charged ions

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2
Q

what is the effect of atomic radius on the strength of an ionic bond?

A

electrostatic attraction gets weaker with distance ∴ the bigger the ion the weaker the bond and lower melting/boiling point

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3
Q

what is the effect of ionic charge on the strength of an ionic bond?

A

greater charge=stronger bond ∴ higher melting/boiling point

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4
Q

how does charge density affect an ionic bond?

A

high charge density form stronger ionic bonds than low charge density

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5
Q

what is an isoelectronic ion?

A

ions of different elements with the same amount electrons

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6
Q

why does ionic radius increases down a group?

A

there is an increasing number of electron shells

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7
Q

why does ionic radius decrease as the atomic number increases?

A

more protons in the nucleus=increased attraction for electrons which brings them closer to the nucleus

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8
Q

what is electronegativity?

A

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

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9
Q

what is metallic bonding?

A

strong electrostatic attraction between metal ions and the delocalized electrons

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10
Q

what is a covalent bond?

A

strong electrostatic attraction between two nuclei and the shared electrons between them

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11
Q

what does molecular shape depend on?

A

-type of electron pairs around the central atom

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12
Q

what is the order of the size of angles in molecules depending on electron pairs?

A

lone/lone pair>lone pair/bonding pair>bonding pair/bonding pair

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13
Q

what is the relationship between bond length and bond strength in a covalent bond?

A

higher electron density=stronger bond=shorter bond

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14
Q

what are giant lattices present in?

A

ionic solids, covalently bonded solids, solid metals

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15
Q

what is the structure of diamond?

A

each carbon atom bonded to its four neighbours in tetrahedral arrangement

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16
Q

what is the structure of graphite?

A

carbon atoms form sheets with each carbon atom sharing three of its outer shell electrons with three other carbon atoms

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17
Q

how does graphite conduct electricity?

A

the fourth outer electron of carbon that is not bonded to the sheets is delocalized ∴
it moves freely between the sheets making graphite a conductor

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18
Q

what is the structure of graphene?

A

-each carbon atom has 3 covalent bonds and one delocalized electrons
-single layer

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19
Q

what is the strongest intermolecular force?

A

hydrogen bonding

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20
Q

when does hydrogen bonding only happen?

A

with highly electronegative elements- O N F

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21
Q

why is ice less dense than water?

A

in ice, water molecules are arranged so that there is a maximum amount of hydrogen bonds which forms a lattice with lots of space between molecules making it less dense

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22
Q

what is dative bonding?

A

when one atom donates both electrons to a bond

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23
Q

how many electrons are in the outer shell of aluminium AlCl3?

A

6

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24
Q

what is the evidence behind the attraction of ionic compounds being very strong?

A

the structures have high melting points

25
Q

what is the evidence behind particles in ionic compounds being charged?

A

often soluble in water (polar substance)–the ions are pulled apart,, but not in non-polar substances

26
Q

what is the evidence behind ions being in a fixed position held by ionic bonds?

A

ionic compounds don’t conduct electricity as solids but do when molten/dissolved

27
Q

what is the evidence behind the lattice model?

A

ionic compounds can’t be shaped

28
Q

what is the bond length?

A

the distance between the two nuclei,, this is where the attractive and repulsive forces balance each other

29
Q

why does water have a relatively high boiling point+melting point?

A

it has hydrogen bonds which are stronger than London forces therefore more energy is needed to overcome these forces

30
Q

why are substances with hydrogen bonds soluble in water?

A

they can form hydrogen bonds with the water molecules

31
Q

why is the boiling/melting point of water unusual?

A

it has fewer electrons than other compounds containing hydrogen bonds

32
Q

what are the properties of electronegative elements?

A

high nuclear charge and small atomic radii (high charge density)

33
Q

are diatomic molecules polar?

A

no, atoms have equal electronegativities so electrons are equally attracted to both nuclei

34
Q

what is a polar bond?

A

when two atoms with different electronegativities bond causing the bonding pairs to be pulled towards the more electronegative atom ∴ the electrons are spread unevenly so there is a charge across the bond causing a dipole

35
Q

what is a dipole?

A

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

36
Q

greater difference in electronegativity…

A

…more polar bond is because of the larger shift it electron density

37
Q

the bigger the difference in electronegativity….

A

…the more ionic character a molecule has

38
Q

why are some molecules non polar even if they have polar bonds?

A

because they have a symmetrical/linear structure therefore the dipole movements cancel

39
Q

what does a polar bond cause?

A

a dipole

40
Q

what is a dipole?

A

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

41
Q

what is the nature of London forces?

A

random movement of electrons in charge clouds form temporary dipole in the first molecule which causes a second dipole on a neighbouring molecule (domino effect) ,, overall effect is that the atoms are attracted to each other

42
Q

what type of bonding do polar molecules have?

A

permanent dipole-permanent dipole (happen as well as London forces)

43
Q

why do branched carbon chains have a lower melting point?

A

-cant pack closely together
-molecular surface contact is small so fewer London forces form

44
Q

why do straight chain alkenes have high melting points?

A

more electrons interact as they can stack on top of eachother

45
Q

why do longer chain alkanes have stronger london forces and melting points?

A

-more molecular surface contact so electrons can interact more

46
Q

why do molecules with a bigger electron cloud have stronger london forces?

A

bigger exposed electron cloud

47
Q

what is hydrogen attracted to in hydrogen bonds?

A

lone pair of electrons on oxygen, fluorine, nitrogen

48
Q

which organic molecules normally form hydrogen bonds?

A

amines (-NH) and alcohols (-OH)

49
Q

why do alcohols have low volatility compared to alkanes (higher boiling temperatures)?

A

-alcohols have hydrogen bonds due to the polar hydroxyl group
-alkanes only have London forces so less energy is needed to overcome the intermolecular forces

50
Q

why do hydrogen bonds affect how a substance behaves?

A

substances that form hydrogen bonds have high melting points and boiling points because a lot of energy is needed to overcome them

51
Q

how do the boiling points of hydrides (group 7 halogens) vary due to intermolecular forces?

A

-HF forms hydrogen bonds so has the highest BP
-the rest of the hydrides of G7 (HCl-HI) have an increasing number of electrons down the group so strength of London forces increases (it overrides decrease in strength of pdpd)
-(HCl-HI BP increases)

52
Q

when will a substance usually dissolve?

A

if the strength of the new bonds formed is the same or more strong than the bond broken

53
Q

why do ionic substances usually dissolve in polar substances such as water?

A

-due to the partial charges in polar substances attracting the cations and anions in ionic substances e.g.water
-ions are pulled away from the ionic lattice by water molecules (this is hydration)

54
Q

why would an ionic substance not dissolve?

A

bonding between ions is too strong (stronger than the bonds they’d form with water molecules)

55
Q

why do alcohols dissolve in polar substances such as water even though its covalent?

A

polar O-H bond in alcohol is attracted to polar O-H bonds in water so hydrogen bonds form between the lone pairs on partial negative oxygen atoms and partial positive hydrogen

carbon chain part of alcohol is not attracted to water so the more carbon atoms there are the lass soluble the alcohol

56
Q

why would some molecules with polar bonds not dissolve in water?

A

-their dipoles are not strong enough to form hydrogen bonds with water e.g. halogenoalkanes
-hydrogen bonding between H2O molecules is stronger than potential bonds formed with halogenoalkanes so they don’t dissolve

57
Q

what substances can halogenoalkanes dissolve in?

A

in polar substances that also like them form pdpd bonds (not hydrogen bonds)

58
Q

why do non-polar substances dissolve best in non-polar substances?

A

-they have London forces between their molecules so form similar bonds with the non-polar substance

59
Q

why don’t non polar substances dissolve in water?

A

water molecules are more strongly attracted to eachother than they are to non-polar substances

A Level Chemistry- KE (15 decks)

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