T1- p Block LP3

Question 1

How are elements in group 13 called?

Answer 1

Triels

Question 2

What is electron deficiency?

Answer 2

There are fewer electrons than the number of valence erbitals.

Question 3

What is inner pair effect on +1 oxidation state in group 13?

Answer 3

+1 oxidation becomes more stable down the group.

Question 4

What are the elements in group 13?

Answer 4

Boron, aluminium, gallium, indium, thallium.

Question 5

What is general electron configuration for group 13?

Answer 5

ns² np¹

Question 6

Why group 13 compounds are Lewis acids?

Answer 6

Because they are electron deficient they can accept electrons very easily.

Question 7

Why EX₃ formula copmounds are good catalysts?

Answer 7

They can form a dative bond with Lewis bases that can keep forming and breaking easily.

Question 8

What is amphoteric compound?

Answer 8

It is a compound that is able to react as a both base and an acid.

Question 9

Why diboron trioxide is added to glass?

Answer 9

to improve its thermal properties

Question 10

What is common reducing agent containing boron?

Answer 10

Sodium borohydride, NaBH₄

Question 11

Describe structure of borax, also known as disodium tetraborate.

Answer 11

Crystals of borax contains dianions with a tetrameric structure of four units of boron hydroxide. Two of four boron units have trigonal planar geometry, while the other two have tetrahedral geometry.

Question 12

What is the order of Lewis acid strengths of boron halides?

Answer 12

BI₃> BBr₃ > BCl₃ > BF₃

Question 13

How BF₃ participate in π bonding?

Answer 13

Electrons are donated from full p orbital of F into the vacant p orbital on B.

Question 14

Why BI₃ is a strongest lewis acid from boron halides?

Answer 14

Because bonds are getting longer and overlap between p orbitals getting less favourable as we move atoms apart.

Question 15

Why non fluoride halides prefferes dimerisation to π- bonding?

Answer 15

Because of the poor overlap between halogen and group 13 elements due to large diffuse orbitals.

Question 16

What is dimerisation?

Answer 16

The chemical reaction that joins two molecular subunits, resulting in the formation of a single dimer.

Question 17

What is molecular formula when boron reacts with hydrogen to form boron hydride and why?

Answer 17

B₂H_6, forms electron deficient dimer because B cannot form π- bond with H as H has no lone pairs.

Question 18

Why in this molecule B-H-B bond is 3 centre- 2 electron bond?

Answer 18

It is because we have two sp³ hybrid orbitals on each B and two 1s orbitals from two bridging hydrogen atoms. We get 12 valence electrons, 8 used is forming the four terminal B-H bonds and 4 electrons are left to form two B-H-B bonds. So 2 electrons are delocalised across each B-H-B bond.

Question 19

What is stability trend of the group 13 hydrides?

Answer 19

Stability decreases going down the group.

Question 20

How to make aluminium hydride?

Answer 20

By adding alcohol groups to aluminium

Question 21

What PSEP stands for?

Answer 21

Polyhedral Skeletal Electron Pairs

Question 22

What is Wade’s rule?

Answer 22

A system based on Mo therory foe predicting the structure of a boron hydride by working out the number of pairs or electrons for cluster bonding.

Question 23

What are the steps to find boron hydrides structure?

Answer 23

1. Each BH unit donates two electrons
2. Each H atom donates one elctron
3. Add in any overall charge on the molecule
4. Add up the number of electrons
5. Calculate verticles n-1
6. Count up the number of B-H units
7. Place any remaining H as bridging H’s around open face

Question 24

Using Wade’s rules when structure is closed?

Answer 24

When number of BH units are equal to the number of vertices.

Question 25

Using Wade’s rules when structure is nido?

Answer 25

When number of BH units is one less than the number of vertices.

Question 26

Using Wade’s rules when structure is arachno?

Answer 26

When number of BH units is two fewer than the number of vertices.

Question 27

What are the names of the structures?

Answer 27

1. closed
2. nido
3. arachno

Question 28

Why we can use Wade’s rules to work out the structures of carboranes?

Answer 28

Because B-H and C-H are interchangeable.

Question 29

B-H and C-H⁺ fragments are said to be isolobal. What does it mean?

Answer 29

They have the same number of electrons- isoelectronic.

Their frontier orbitals have the same symmetries, are of similar energy and are the same shape.

Question 30

What is the most stable structure and why?

Answer 30

1,5. Because the most thermodynamically stable isomer is that with the two carbons apart.