P-Block

• Aluminium and lead form amphoteric oxides and hydroxides which react with both acids and bases.
• The reaction of sodium hydroxide with solutions containing metal compounds is used as a test to show if the solution is amphoteric.
• If the solution forms a precipitate on addition of hydroxide, which is then able to redissolve in excess hydroxide, the compound is amphoteric.
• The tendency of the outermost s 2 pair of electrons in an atom to remain unshared in compounds, leading to a lower oxidation state, occurs in groups 3, 4 and 5.
• As you go down a group, the tendency of the outermost s 2 pair of electrons to remain unshared in compounds increases.
• In Group 3, Tl forms Tl + , in Group 4, Pb forms Pb 2+ and in Group 5, Bi forms Bi 3+ .
• The ability of some atoms to use d-orbitals to have more than 8 electrons in their valence (outer) shell explains why period 2 elements can only form compounds with eight outer shell electrons, but period 3 elements can form compounds with more than 8 electrons in their outer shell.
• Reactions of Group 4 chlorides with water are a characteristic of these elements.
• Amphoteric behaviour is a characteristic of Group 4 elements.
• Properties of CO2 and PbO are related to Group 4 elements.
• Reaction of Cl2 with NaOH is a characteristic of Group 7 elements.
• Uses of chlorine and chlorate(I) ions are related to Group 7 elements.
• Reaction of sodium halides with conc H2SO4 is a characteristic of Group 7 elements.
• Graphite and hexagonal BN are compounds of Group 3 and Group 5 elements.
• Stability of oxidation states in Group 4 is a characteristic of these elements.
• Diamond and cubic BN are compounds of Group 3 and Group 5 elements.
• Electron deficiency in Group 3 is a characteristic of these elements.
• Boron nitride, BN, is a compound of Group 3 and Group 5 elements.
• Inert pair effect is a phenomenon associated with Group 3 elements.
• Octet expansion is a concept related to Group 3 elements.
• Reactions of Pb2+ (aq) are a characteristic of Group 7 elements.
• Nitrogen’s only chloride is NCl 3 but phosphorus can form PCl 3 or PCl 5 ; phosphorus has access to d-orbitals, which can accommodate more electrons, so there is no longer a limit of 8 electrons in the outer shell.
• Nitrogen has no access to d-orbitals so cannot expand its octet.
• When group 3 elements form covalent compounds, they only form 3 covalent bonds.
• This only gives 6 electrons in the outer shell, which causes electron deficiency.
• To fill the shell, group 3 elements form co-ordinate bonds to gain extra electron pairs.
• Aluminium chloride forms a dimer.
• BF 3 NH 3 forms a donor-acceptor compound.
• The electron deficient BF 3 accepts a lone pair from the NH 3 .
• Both BN and carbon have the same number of electrons, 12, which is known as isoelectronic.
• Both BN and carbon have high melting points due to strong covalent bonds between the atoms.
• BN is used as a wear-resistant coating.
• Forces between layers in both BN and graphite are weak, allowing layers to slide over one another.
• The stable chlorides of carbon and silicon are the tetrachlorides, which are covalently bonded colourless liquids.
• The stable chloride of lead is lead(II) chloride, which is an ionic solid.
• Graphite, on the other hand, contains delocalised electrons and can conduct electricity, making it useful as a lubricant.
• The stability of the +2 state increases as you go down the group, due to the inert pair effect becoming more significant.
• PbO is an orange solid which contains ionic bonding and is an amphoteric oxide, reacting with acids and bases.
• CO is easily oxidised to CO 2 (changes from +2 to +4), making it a reducing agent.
• CCl4 and SiCl 4 should react with water, but PbCl 2 will not.