Abnormal Behaviour Of First Elements to their respective groups..

 

         

         .Abnormal  Behaviour Of  First Elements to their respective groups.

 

Reasons  for their abnormal  behaviour .

 

   i- Small size   ii- High electronegativity   iii-  High ionization energy   iv- If the first              element is metal, they have high polarizing power.  

                              

 

• Ø Abnormal behaviour of   ‘ Li’  to its respective group .

 

·        It is much harder then other elements of group.

·        It has high melting and boiling point .

·        Due to high polarizing power .

·        Salts of  ‘Li’  are soluble in organic solvents.

·        ‘Li’ is the only element which can combine with ‘N’ and ‘Si’.

·        It can not react  with  O₂  at low temperature  and react slowly with  H₂O .

·        It is least reactive element of its group .

·        It can form normal oxides usually while other form super and per oxides .

·        When Acetylene is passed over Li , it does not form acetylides.

     

·        Carbonates  of  ‘Li’ are unstable to heat.

        Li₂Co₃    +   heat              =                Li₂O   +  CO₂

·        Hydroxides of Li are unstable .

·        Nitrates of all IA  elements  are all unstable  but on decomposition give different

product .

·        LiOH is less basic due to high covalent character.

 

• Ø Abnormal behaviour of  Be to its respective group .

 

·        It is hard then other respective  group elements.

·        It has covalent character due to high polarizing power .

·        It gives slow reaction reaction to with H₂O  and  O₂.

·        It react with alkalies  . Be   +  NaOH      =      Na₂Be₂O₂    + H₂

·        Its oxides are amphoteric in nature .

Be   +  NaOH                     =               Na₂Be₂O₂   + H2

BeO   +   H₂SO_{4                         =}                  BeSO₄     + H₂O

 

·        Its hydroxides are less basic .

·        Nirides are volatile in nature .

·        Its compounds contain water of crystallization .it contains maximum  4 molecules of water of crystallization .

·        It forms complex .  [ BeF₄]^-2.

 

• Ø Abnormal behavior of ‘ B’  to its receptive group .

 

·        B is non metal while other elements of group are metals .

·        Its compounds are negative .

·        Its compounds have strong tendency to accept electrons and act as Lewis acids

·        Its maximum co-valency is 4 but other has up to 6 or more .

 

• Ø Abnormal behavior of  ‘C’ to its respective group .

 

·        It is hard .e.g . diamond .

·        It has high melting and boiling point.

·        CCL₄  can’t be hydrolyzed.

·        It can not from complex ions.

·        CCL₄ can nit give addition compounds.

·        Its co-valency is 4 but other have 6 or more .

·        Oxide of C  are present in gas state but  SiO₂ is present in solid form.

·        It shows catenation .

·        There is  p__p  overlapping .

·        There is no inert pair effect .

·        C and Si are only non metals.

 

• Ø Abnormal behaviour of  ‘N’ to its respective group.

 

·        Present in free and combined state but other members present in combined form .

·        It cannot from complex due to absence of  d-orbital.

·        N  is gas at room temperature but other members are solid at room temperature.

·        It has maximum co-valency 4 but other  have 6 or more .

·        It shows   numbers  in oxidation  numbers but other members  show limited  oxidation  no.

·        Catenation is found in N but other members don’t show .

·        Hydrides of  N are stable  and non poisonous.

·        Hydrides of  N  can polymerize .

·        N forms oxides in large numbers .

·        Oxides of  N are monomeric .

·        N is inert gas.

·        N can form   NCL₅  ,  NBr₅ .

·        P ___ P overlapping is present in N  but absent in others.

 

• Ø Abnormal  behaviour of  'O'  to its respective group .

 

·        Its atomicity is 2.

·        It can easily form  M^-2   ions  due to high electronegativity.

·        Its normal oxidation number is -2 but  +2 in OF₂ . Other will show +2,+4,+6.

·        Its maximum covalency is 2.

·        It can form hydrogen bonding.

·        It has tendency for p__p overlapping and multiple bonding.

·        It shows  paramagnetic property.

 

• Ø Abnormal behaviour of  'F'  to its respective group.

 

·        Its oxidation state is only -1.

·        It can form only  OF₂  but other can give multiple oxides .

·        It can form interhalogen compounds .

·        Oxyacids of  F are not formed.

·        Its covalency is 1 but other members  can show up to 7.

·        F___F   has low bond association  energy .

·        Its is highly reactive element.

·        F  can not form polyhalides.

·        SF₆ ( sulphur hexa fluoride ) can be formed but other sulphur hexa halides can not be formed .