Titanium, Zirconium and Hafnium Group IVA

The Gp. IVA transition elements, titanium, zirconium and hafnium all have the [n — l)d2ws electron configuration. They differ from the transition elements of the later groups in their tendency to form compounds to the exclusion of those in which lower charge numbers occur especially is this true of Zr and Hf. 

The atomic and ionic radii of Hf are very close to those of Zr, in spite of  

The first ionisation potentials are all fairly low and those for ionisation up to arc known. As usual, the small 4+ ion which is invoked in compounds does not exist as such, but takes a considerable share of the electron density of the ligands. Nor does the ion exist in aqueous solution the most stable cation is the complex ion MO + and the redox potentials above refer to the MO2+/M couples. The metals are evidently strongly reducing but they are so easily rendered passive that they are not very reactive at room temperature and have a remarkable resistance to corrosion. 

The elements, as many true metals, have h.c.p. lattices. Their atomic radii and atomic volumes are similar, especially those of zirconium and hafnium. As the atomic weight of Hf (178.6) is almost twice that of Zr (91.2) their densities differ by a factor of two. Titanium is not only much less dense than Zr but so than succeeding elements of the first transition series. The metals are typical transition elements in their high m.p. and b.p. 

Titanium (0.6% of the earth s crust) is abundant but difficult to extract. It is commonly associated with siliceous rocks, but the principal workable 

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