structure

Question 1

electronegativity is

Answer 1

power of an atom to attract the pair of electrons in a covelant bond towards itself

Question 2

when does uneven electron distribution occur

Answer 2

when the elements in a covelant bond have different electronegativities

Question 3

most electronegative atom

Answer 3

fluorine

Question 4

nuclear charge affect on electronegativity and why

Answer 4

increasing charge causes increasing electronegativity

attraction exists between positive protons and negative electrons in energy levels of an atom

more protons = greater nuclear attraction of these electrons

Question 5

atomic radius affect on electronegativity and why

Answer 5

increasing radius decreases electronegativity

electrons further from the nucleus are less strongly attracted to the nucleus

Question 6

shielding affect on electronegativity and why

Answer 6

filled energy levels shield the effect of nuclear charge reducing the attraction between outer e- and nucleus

increased number of inner shells and subshells results in a decreased electronegativity

Question 7

down a group affect on electronegativity and why

Answer 7

decrease in electronegativity down the group

although nuclear charge increases

increased shielding with the addition of extra e- shells this means there is also a…

larger atomic radius

Question 8

across a period affect on electronegativity and why

Answer 8

electronegativity increases across a period

nuclear charge increases with increasing proton number

shielding remains relatively constant

smaller atomic radius

Question 9

what dictates if a molecule will be polar

Answer 9

if there is a difference in the electronegativities

Question 10

what dictates what type of bond is formed

Answer 10

difference in electronegativities

Question 11

what electronegativity difference is covelant bond

Answer 11

0.3 to 1.7

atoms will get a partial charge

Question 12

which atom are electrons drawn to

Answer 12

the more electronegative one

atoms will get a partial charge

Question 13

how to identify if a molecule is polar

Answer 13

polar bonds can be arranged in a way which will cancel out the polarity

if the shape is symetrical then the molecule wont be polar

Question 14

order of strength of IM forces and bonds

Answer 14

weaknesses to strongest

dipole dipole (indiced)
dipole dipole (permanant)
hydrogen bonds
covelant bond

Question 15

how do induced dipoles occur

Answer 15

random dipole occurs from a shift in electron cloud of a non polar molecule

this dipole moves towards another molecule

and induced dipole forms with opposite charge of the temporary dipole

Question 16

how do permanent dipoles form

Answer 16

between two polar molecules - force between opposite partial charges

Question 17

how do hydrogen bonds form

Answer 17

between a O, N or F atom and hydrogen (basically a really strong form of dipole)

Question 18

what is the number of hydrogen bonds that can form dependent on

Answer 18

number of lone pairs of electrons on the negative

Question 19

why does water have high melting point

Answer 19

strong hydrogen bonds between molecules which require a lot of energy to overcome

Question 20

why does heat required to vaporise a molecule increase with increased number of electrons

Answer 20

increased instantaneous dipole to induced dipole forces

Question 21

why does water have a high surface tension

Answer 21

water molecules at the surface of liquid are bonded to other water molecules through hydrogen bonds

bonds pull downwards causing the surface to be compressed and more tightly together at the surface

Question 22

how does branching affect the strength of London forces

Answer 22

surface area of molecule is reduced
therefore as branching decreases london force strength increases

Question 23

how does number of electrons affect the strength of dipole dipole

Answer 23

more electrons results in a greater likelihood of distortion and therefore a greater frequeny and magnitude of temporary dipoles

which would result in a higher mp and bp

Question 24

why are alcohols very high mp and bp

Answer 24

oh present thus as hydrogenb has partial + and oxygen partial - , hydrogen bonding can occur which requires lots of energy to overcome compared to just temporary induced dipoles in alkanes

Question 25

trend in the boiling points of the hydrogen halides and why

Answer 25

genrally increases as the molecules become larger (halide down the group)

extra electrons llow greater temporary dipoles so the london dispersion forces are increased between the molecules

HOWEVER

HF has fluorine which is very electronegative (and has a lone pair) so the bond is very polar and hydrogen bonds can form

Question 26

what happens to the solubility of covelant molecules as they become larger

Answer 26

the polar part of the molecule will be smaller therefore solubility decreases

Question 27

why cant non polar substances dissolve in polar substances

Answer 27

dipole-dipole interactions are unable to occur well in the substance .