The transition elements

PHYSICAL PROPERTIES OF THE FIRST TRANSITION SERIES ELEMENTS 

It is immediately obvious that the transition metals are more dense, harder, and have higher melting points and boiling points than the main group metals (for example, the metals of Group II, 

FURTHER PHYSICAL PROPERTIES OF TEE FIRST TRANSITION SERIES ELEMENTS 

The transition elements are often said to exhibit variable valency. Because they so readily form complex compounds, it is better to use the term variety of oxidation states . The states usually found for the elements Sc-Zn are  

We may note (a) the common occurrence of oxidation state +2 where the 4s electrons have been formally lost, (b) the increase in the number of oxidation states from scandium to manganese in the latter element, the oxidation state + 7 corresponds to the formal loss of the and 3d electrons, (c) the sharp decrease in the number of oxidation states after manganese—suggesting that removal of the paired id electrons is less easy (d) the oxidation state 0, occurring for many of the later elements in the series.  

F igure 13.1. Graph oj h.p. against atomic number Jor the Jirst transition series 

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As regards the transition elements, the first row in particular show some common characteristics which define a substantial part of their chemistry the elements of the lanthanide and actinide series show an even closer resemblance to each other. 

Some of the oxidation states given above, especially the higher oxidation states (7, 6) and oxidation state 0, are found only when the metal atom or ion has attached to it certain groups or ligands. Indeed the chemistry of the transition elements is so dominated by their tendency to form coordination complexes that this aspect of their behaviour must be considered in some detail. 

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