topic 2

Question 1

what are isoelectronic ions

Answer 1

atoms, ions or molecules that have the same electronic configuration/structure

Question 2

what is the trend in ionic radii of a set of isoelectronic ions across a period

Answer 2

if the number of protons increase electrons are more attracted to the nucleus
so ionic radii falls

Question 3

what provides evidence for the existence of ions

Answer 3

1- physical properties such as electrical conductivity, ionic substances are brittle
2- electron density maps
3- migration of ions using copper (III) dichromate

Question 4

how does the migration of ions prove the existence of ions

Answer 4

copper ions are blue and positive -> attracted to cathode
dichromate ions are orange and negative -> attracted to the anode

Question 5

what is a covalent bond

Answer 5

strong electrostatic attraction between two nuclei an the shared pair of electrons between them

Question 6

recall the names of shapes of molecules

Answer 6

linear
trigonal planar
bent
tetrahedral
trigonal pyramidal
trigonal bipyramidal
octahedral
square planar
T shape
seesaw
square pyramid

Question 7

how many bonding/lone pairs does a linear molecule have- draw the shape and label the bond angle

Answer 7

2 bond pairs
180 degrees

Question 8

how many bonding and/lone pairs does a trigonal planar molecule have- draw the shape and label the bond angle

Answer 8

3 bond pairs
120 degrees

Question 9

how many bonding and/lone pairs does a bent molecule have- draw the shape and label the bond angle

Answer 9

1 lone pair
2 bond pairs
<120 degrees

or

2 bond pairs
2 lone pairs
<109 degrees

refer to VESPR table for shape

Question 10

how many bonding and/lone pairs does a tetrahedral molecule have- draw the shape and label the bond angle

Answer 10

4 bond pairs
109 degrees

Question 11

how many bonding and/lone pairs does a trigonal pyramidal molecule have- draw the shape and label the bond angle

Answer 11

3 bond pairs
1 lone pair
<109 degrees

Question 12

how many bonding and/lone pairs does a trigonal bipyramidal molecule have- draw the shape and label the bond angle

Answer 12

5 bond pairs
90 and 120 degrees

Question 13

how many bonding and/lone pairs does a seesaw molecule have- draw the shape and label the bond angle

Answer 13

1 lone pair
4 bond pairs
<120 degrees and <90 degrees

Question 14

how many bonding and/lone pairs does a T shape molecule have- draw the shape and label the bond angle

Answer 14

2 lone pairs
3 bond pairs
<90 degrees

or

3 bond pairs
3 lone pairs
<90 degrees refer to VESPR table for shape

Question 15

how many bonding and/lone pairs does an octahedral molecule have- draw the shape and label the bond angle

Answer 15

6 bond pairs
90 degrees

Question 16

how many bonding and/lone pairs does a square pyramidal molecule have- draw the shape and label the bond angle

Answer 16

1 lone pair
5 bond pairs
<90 degrees x2

Question 17

how many bonding and/lone pairs does a square planar molecule have- draw the shape and label the bond angle

Answer 17

2 lone pairs
4 bond pairs
90 degrees

Question 18

what causes bonds to be polar

Answer 18

electronegativity differences as electrons in the bond arent shared equally

Question 19

how can you predict whether a molecule is polar

Answer 19

whether the molecule is symmetrical
whether the molecule has polar bonds

Question 20

how do london forces form

Answer 20

caused by an uneven distributions of electrons within an atom
this results in a slight negative and slight positive charge on either side of the atom -> temporary dipole
this temporary dipole can induce a temporary dipole on a neighbouring molecule

Question 21

how does a permanent dipole force arise

Answer 21

the forces are between the slightly positive end of one polar molecule and the slightly negative end of another polar molecule
the slight charges are due to permanent dipoles which arise when theres an electronegative atom or a halogen

Question 22

how do hydrogen bonds arise

Answer 22

they result from the attractive force between a hydrogen atom, which is covalently bonded to a very electronegative atom, and another very electronegative atom

Question 23

how does hydrogen bonding arise in water

Answer 23

hydrogen bonds form between neighbouring hydrogen atoms and oxygen atoms of adjacent water molecules

Question 24

how does hydrogen bonding arise between ammonia (NH3) molecules

Answer 24

electronegativity difference between hydrogen and nitrogen which means that a partial charge develops on them

Question 25

why does water have a relatively high bpt

Answer 25

due to hydrogen bonding requires more energy to overcome as its the strongest I force

Question 26

why is ice less dense than water

Answer 26

this is because when hydrogen bonds form it pushes water molecules further apart which decreases the density

Question 27

what is the trend in boiling temperatures of alkanes with increasing chain length

Answer 27

stronger/increased number of london forces as theres more electrons in longer chained alkanes

Question 28

what is the effect of branching in the carbon chain on boiling temperatures of alkanes

Answer 28

as branching increases, the surface area of the molecule decreases smaller area of contact london forces decrease therefore bpt decreases

Question 29

why are alcohols less volatile compared to alkanes with a similar number of electrons

Answer 29

this is because alcohols can form hydrogen bonds between molecules whereas alkanes only form london forces which are weaker

Question 30

what does volatile mean

Answer 30

a substance that is readily changing from a solid or liquid to a gas

Question 31

why is water a good solvent for some ionic compounds

Answer 31

ions attracted to the water molecules ions hydrated

Question 32

why is water used to dissolve simple alcohols

Answer 32

water can form hydrogen bonds with them

Question 33

why is water a poor solvent for polar molecules and halogenoalkanes

Answer 33

this is because they cant form hydrogen bonds with water

Question 34

when are non aqueous solvents used

Answer 34

used for compounds that have similar intermolecular forces to those in the solvent

Question 35

why are non polar substances soluble in hexane and not water

Answer 35

- insoluble in water as it cant hydrogen bond to water - this is because none of the hydrogen atoms in the non polar substance have a slight positive charge - its soluble in hexane because the london forces in the substance and hexane are similar in strength

Question 36

why are ionic/ polar substances soluble in water and not hexane

Answer 36

ionic substances ions are hydrated the enthalpy of hydration is greater than the energy needed to break apart the lattice its insoluble in hexane because any london forces that form between the ionic substance and hexane will be smaller in size than the forces between the ions in the ionic/polar substance