. Compare the general characteristics of the first series of the transition metals with that of the second and third series metals in the respective ver


Compare the general characteristics of the first series of the transition metals with that of the second and third series metals in the respective vertical columns. Give special emphasis on the following points:

(i) Electronic configuration 

(ii) Oxidation states

(iii) Ionisation enthalpies 

(iv) Atomic sizes. 

 

Best Answer

(i)         Electronic configuration The elements in the same vertical column generally have similar electronic configurations. Although the first series has only two exceptions

(a)        Cr = 3d5 4s1 and (b) Cu = 3d104s1

Second transition series has five exceptions

(a)        Mo = 4d55s1;                (b)        Nb = 4d45s1;

(c)        Rh = 4d85s1                     (d)        Pd = 4d105s1

Third transition series have three exceptions:

(a)        W = 4f14 5d46s2;           (b)        Pt = 4f145d96s1;

(c)        Au = 4f14 5d106s1

(ii)        Oxidation states The elements in the same vertical column generally show similar oxidation states. The number of oxidation states shown by the elements in the middle of each series is maximum and minimum at the extreme ends. 

(iii)       Ionisation enthalpies The first ionization enthalpies in each series generally increase gradually as we move form left to right though some exceptions are observed in each series. The first ionization enthalpies of some elements in the second (4d) series are higher while some of them have lower value than the elements of 3d series in the same vertical column. 

However, the first ionization enthalpies of (third transition series (5d series) are higher than those of 3d and 4d series. This is because of weak shielding of nucleus of 4f electrons in the 5d series. 

(iv)       Atomic size Generally, ions of the same charge or atoms in a given series show progressively decrease in radius with increasing atomic number though the decrease is quite small. But the size of the atoms of the 4d series is larger than the corresponding elements of the 3d series whereas those of corresponding elements of the 5d series are nearly the same as those of 4d series due to lanthanoid contraction. 

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