3.3 Chemistry of the P block

Group 3 elements have oxidation states of…

3 and 1

Group 4 elements have oxidation states of…

4 and 2

Group 5 elements have oxidation states of…

5 and 3

two things that determine which is the more stable of the two oxidation states

inert pair effect 

octet expansion 

Octet expansion

the ability of atoms to use their d-orbitals so that they can have more than 8 electrons in their outer shell

examples of octet expansion

PCl5

SF6

ClO4 -

inert pair effect

the reluctance of s electrons to take part in bonding

result of the inert pair effect 

The lower oxidation states are more stable the lower down the group you go

amphoteric

something that reacts with both acids and bases

examples of amphoteric elements

aluminium

zinc

lead

electron deficiency

fewer than 8 electrons in outer shell

what do electron deficient compounds do

form co-ordinate bonds with a lone pair of electrons from another atom

what does aluminium chloride do

forms a dimer of Al2Cl6

what does boron trifluoride accept a lone electron pair from

Nitrogen in ammonia

differences between graphite and hexagonal boron nitride 

Layers in BN are directly above each other with no delocalised electrons. Layers in graphite don’t have atoms directly above each other

No delocalised electrons in BN, whilst there are in graphite, so BN cannot conduct electricity.

BN is used as an electrical insulator

use of hexagonal boron nitride nanotubes

can be wrapped around a carbon nanotube and act as an insulating layer, thereby ensuring that the electrical current cannot escape

property of carbon monoxide

reducing agent e.g in the blast furnace

property of lead(IV) oxide

oxidising agent

carbon dioxide is an…

acidic oxide as it will only react with bases

lead oxide is…

amphoteric. It will react with acids and bases

does carbon tetrachloride react with water

no, it simply forms a separate liquid layer

does silicon tetrachloride react with water

yes, reacts quickly and quite violently with water, forming a white solid of silicon dioxide and cloudy fumes of HCl

why does silicon react with water but carbon doesn’t 

Availability of d-orbitals in the silicon atom allows a lone pair from oxygen to bond

These d-orbitals don’t exist in the carbon atom, so it cannot react in the same way

2 soluble lead salts

lead (II) nitrate

lead (II) ethanoate

observation of adding OH- ions to lead (II) solution

white lead hydroxide precipitate formed

observation of adding excess OH- ions to lead (II) solution

White precipitate dissolves to form a colourless solution containing the plumbate ion 

observation of adding Cl- ions to lead (II) solution

heavy white lead chloride precipitate formed 

observation of adding I- ions to lead (II) solution

bright yellow lead iodide precipitate formed

oxidising power of halogens

decreases down the group

chlorine is the strongest oxidising agent, whilst iodine is the weakest oxidising agent

Reaction of sodium halides with conc H2SO4

All of the ions react with sulfuric acid to form the sodium hydrogensulfate and steamy fumes of hydrogen halide gas

disproportionation 

atoms of the same element become oxidised and reduced to form different products

reaction of chlorine with cold NaOH

form sodium chloride and sodium chlorate(I)

reaction of chlorine with warm NaOH

sodium chloride and sodium chlorate(V) are formed

chlorine and chlorate ions are…

oxidising agents

use of chlorine 

used in water supplies 

use of chlorate

bleach