inorganic 6- groups 13&14&15 [ruth]

Question 1

Group 13 halides are
-Lewis acids/lewis bases
-and what formula do they usually take
- do they want to give or take electrons

note- halides have halogen in them

Answer 1

+3 oxidation state
-want to take electrons

Question 2

how many valent electrons do elements in group 13 have

Answer 2

6 VE ?

Question 3

will a B-I or B-F bond be longer

Answer 3

B-I is longer
bond length increases from F –> I

Question 4

BF4- is weakly/strongly co-ordinating

Answer 4

weakly

Question 5

BF3 is sp2 hybridised. Why is this compounds stable?

Answer 5

double bond character with the flourines
-F’s have lone pairs of electrons which they can donate towards the B

Question 6

Why can BF3 react with Lewis bases [electron donating species]

Answer 6

B has an empty p orbital
-Lewis base can donate electrons to this orbital
-will co-ordinate well if the size of B’s p orbital is similar to the size of the orbital that contains the lone pair of electrons on the base

Question 7

what are “adducts”

Answer 7

where there isn’t a formal covalent bond between the species [in this case B and O], it is instead an interaction of a lone pair of electrons with a p orbital

Question 8

will L.BF3, L.BCl3, or L.BBr3 be more stable [The L is to do with the adduct formed]

Answer 8

L.BBr3
-BF3 has good overlap and is the most stable compound, so it is less happy to go from this to L.BF3
-BBr3 has the least good overlap between bonding orbitals, so is more happy to go to its adduct state

Question 9

you would expect L.BF3 to be the most stable because BF3 is the more stable compound [compared to BCl3 and BBr3]
-why is this not the case and actually L.BBr3 is the most stable

Answer 9

When L co-ordiantes it changes sp2 to sp3
-means π interactions are lost
-bigger energy loss/deficit going from BF3 to L.BF3 than from going from BBr3 to L.BBr3

Question 10

Answer 10

i)

Question 11

is Al(OH)3 is amphoteric
-how does it react with an acid and a base (H3O or OH)
-base forms aluminate ion

Answer 11

Question 12

how many bonds does Al usually form

Answer 12

4

Question 13

group 14 halides have what form (e.g. EX3)
-it is different for carbon and silicon than it is for Sn and Pb

Answer 13

EX4 for all
EX2 for PB and Sn due to the inert pair effect

Question 14

which is more prone to attack by nucleophiles and why carbon or silicone

Answer 14

silicone- because it is bigger

Question 15

what is the trend in each of these things as you go across the table

Answer 15

all increase except radii

Question 16

what is the trend in each of these things as you go down the table

Answer 16

Question 17

are the electron affinity energies high or low for the highlighted elements

Answer 17

Question 18

Answer 18

Question 19

+3 and +1 are the most common oxidation states for group 16
-lower oxidation state is more stable lower down the group
-why is this

Answer 19

lower down the group you don’t have access to the s orbitals in order to form bonds
so the 2s electrons stay as an inert pair

Question 20

the inert pair effect- why do the 2s electrons stay as an inert pair when elements far down the table bond

Answer 20

weak bonds- not a lot of energy is got back from making bonds bc the bonds are weak
promotion E- takes a lot of E to promote 2s to become bonding electrons, and this energy isn’t gotten back due to the weak bond formation

why takes more energy need to know- 2s orbitals become more diffuse and higher energy going down group and are penetrating closer to the nucleus

Question 21

what is catenation

Answer 21

covalent bonding of 2 or more atoms of the same element to each other

Question 22

explain these qualities of row 2 elements
-catenation
-allotropy
-multiple bonds (π bonds)

Answer 22

catenation- its ability to form a covalent bond with itself

Question 23

octet rule is obeyed for row 2 elements

Question 24

what are the row 2 elements general (and max) co-ordination number

Answer 24

4

Question 25

why are **row 2 elements not very reactive** compared to other rows (e.g. why is CCl4 less reactive than SiCl4)

Answer 25

X= electronegativity

Question 26

for all of the periodic table - where has the most covalent vs ionic character

Answer 26

most **covalent character at top** most ionic character at bottom

Question 27

are group 14 EX4 halides usually reactive

Answer 27

unreactive

Question 28

which is more stable, PbX2 or PbX4 where X= halide -and why

Answer 28

PbX2 is more stable due to the fact that it is more stable for Pb to form an oxidation state of 2+ than 4+ -inert pair effect [2s electrons stay as inert pair and do not interact in bonding]

Question 29

what 2 elements in group 14 are less reactive than metals in group 1,2 and 13

Answer 29

Sn and Pb

Question 30

Sn and Pb react slowly with concentrated acids -what is the equation and what is the driving process for this reaction

Answer 30

Question 31

is carbon dioxide soluble in water -and what are the 3 equations

Answer 31

yes

Question 32

using bond strengths, explain why CO2 gas is the favoured structure of CO2, yet SiO2 is a network

Answer 32

Question 33

what is the form that silicone likes to take on in any molecule (e.g linear)

Answer 33

tetrahedral with a 109° bond angle

Question 34

what would be the structure of sodium silicate

Answer 34

tetrahedral with a 109° bond angle

Question 35

why is PbO2 a good oxidising agent

Answer 35

PbO2- Pb oxidation state is +4 and it is more stable being +2, so wants to be reduced itself to PbO

Question 36

why are all group 15s lewis bases N, P, As, Sb, Pi

Answer 36

Lewis bases- electron pair donning -because they all have 1 lone pair each and are electron rich

Question 37

which elements out of group 13,14, and 15 usually dont follow the trend

Answer 37

row 2 elements e.g nitrogen

Question 38

what is the structure of -N2 -P4

Answer 38

Question 39

Answer 39

There is a p orbital in Oxygen (π* orbital) that can accept electron density from the phosphorus -reacts to form very strong P=O bonds which is the driving force of the reaction

Question 40

why is dinitrogen very unreactive N≡N

Answer 40

**large homo-lumo gap** preventing oxidation and reduction

Question 41

what does the NO3 - anion look like

Answer 41

Question 42

what is the only molecule where N with an oxidation state of +5 is possible

Answer 42

NO3 - anion (e.g HNO3)

Question 43

what is the structure of NO2

Answer 43

Question 44

what is the structure of N2O2

Answer 44

Question 45

what are the two main oxidation states of P (in group 15)

Answer 45

+3 and +5

Question 46

what is the formula difference between phosphonic acid and phosphoric

Answer 46

Question 47

how do these form polyphospheric acids

Answer 47

Question 48

Answer 48

-indium has an empty p orbital -Sn doesnt have a lone pair -Sb has a lone pair -water has lone pairs 1. therefore In will react best with H2O, Sn will have not very much and Sb will have repulsion with water 2. O2 has 2 unpaired electrons, and it can accept electrons into these orbitals. Therefore won't react with Sn, and will with Sb

Question 49

what is the general formula for halides of group 13 vs 14 vs 15 [e.g in the form EX2]

Answer 49

13= EX3 14= EX4 (except for Pb and Sn EX2) 15= EX3

Question 50

why is NF3 **less basic** than NH3 -

Answer 50

NF3 has very polarised bonds, F is very electronegative so draws the lone pair towards it -so the lone pair is **basically inactive**

Question 51

why is NCl3 more reactive than NF3 with acids/ why is NCl3 more basic

Answer 51

NCl bond is less polarised than NF because Cl is less electronegative than F -so the lone pair are less drawn towards Cl and therefore the lone pair are move reactive

Question 52

NF3 --> NI3 what is the trend in basicity down the halides

Answer 52

gets more basic

Question 53

compare these two reactions of group 15 halogen molecules with water -how is H2O being attacked or doing the attacking?

Answer 53

P-Cl has a much more polorized bond than N-Cl -so the O electrons will attack the δ+ P -in N-Cl the nitrogen loan pair attacks the H δ+ in H2O

Question 54

how is POCl3 formed

Answer 54

Question 55

why can NF5 not exist but PF5 can, despite them both being group 15 elements

Answer 55

N cannot achieve +5 oxidation states with halides but P can

Question 56

In an NMR spec of this molecule you might expect to see 2 signals for 2 different flourine environments [axial and equatorial] -but you only see 1 signal why is this

Answer 56

rapid equatorial/ axial exchange at room temperate

Question 57

as you add halides to elements in group 15, down the table you start to form bridges -what is the structure of this

Answer 57

Question 58

why is there increasing acidity from PH3 to BiH3

Answer 58

-weakening bond strength due to bigger ion/ incompatible overlap between group 15 element and hydrogen 1s orbital -therefore can more easily loose a hydrogen and increasing acidity

Question 59

does a bigger or smaller pka mean a stronger or weaker acid

Answer 59

smaller pka= stronger acid

Question 60

why does PH5 decompose rapidly but PF5 will not

Answer 60

F2 bonds are fairly weak so there isn't the energy payback as PH5

Question 61

why are F-F bonds weak in F2

Answer 61

electron-electron repulsion

Question 62

trend in basicity from NH3 --> BiH3

Answer 62

-both have lone pairs -but Bi is much bigger and N is smaller therefore electron density is much greater on N than it is on B -NH3 has a greater tendency to donate its electrons **decreasing basicity** down the group / lower elements are not very basic at all

Question 63

why can the structure of PH3 get closer to the ideal bond angle than NH3 -N is above P in the periodic table

Answer 63

longer+weaker bonds down the group -N-H bonds are short and strong you get a lot of electron repulsion which pushes the bonds apart -whereas P-H bonds are longer and weaker so they can come closer together P-H bonds are more diffuse and can avoid e-e repulsion

Question 64

name each of the types of bonding for the coloured groups for fluorides -molecular covalent -polar covalent -ionic

Answer 64

polar covalent- down the group the elements become more electropositive and fluorine is very electronegative

Question 65

what is the difference in where the electrons fall on the bond

Answer 65

Question 66

label each chloride as -molecular covalent -polymers -ionic

Answer 66

Question 67

label each oxide as -molecular covalent -polymeric

Answer 67

Question 68

what needs to be the difference in electronegativity between the two atoms to make a bond ionic

Answer 68

1.7

Question 69

what is the reactivity of O2, vs H2O

Answer 69

H2O has lone pairs, which they can donate into empty orbitals O2 has 2 unpaired electrons and can accept 2 electrons also (into the half filled orbitals)