question_answer 116)

     (a) Answer the following questions (i) Which element of the first transition series has highest second ionisation enthalpy? (ii) Which element of the first transition series has highest third ionisation enthalpy? (iii) Which element of the first transition series has lowest enthalpy of atomisation? (b) Identify the metal and justify your answer. (i) Carbonyl (ii)

Answer:

                    (a)   (i) Cu, because the electronic configuration of Cu is . So, second electron needs to be removed from completely filled d-orbital which is very difficult. (ii) Zinc, because of electronic configuration of  and Zn2'1' =  which is fully filled and hence is very stable. Removal of third electron requires very high energy. (iii) Zinc, because of it has completely filled 3d subshell and no unpaired electron is available for metallic bonding. (b)   (i) Carbonyl  is According to EAN rule, the effective number of a metal in a metal carbonyl is equal to the atomic number of nearest inert gas EAN is calculated as EAN =number of electrons in metal +2 x (CO) =atomic number of nearest inert gas          In  = x + 2 x (5) = 36 (Kr is the nearest inert gas)       x = 26 (atomic number of metal) So, the metal is Fe (iron). (ii) In  Let us assume that oxidation state of M is x X + 3 x (-2) + (-1) = 0 Or, x = + 7 i.e., M is in +7 oxidation state of +7. Hence, the given compound is .