Group 4 element doses and does not play any natural role inside the human body. Zirconium powder can cause irritation, but only contact with the eyes requires medical attention. OSHA recommendations for zirconium are 5 mg/m time weighted average limit and a 10 mg/m short-term exposure limit. Only limited data exists on the toxicology of hafnium. Group 4 element Group 4 is a group of elements in the periodic table. It contains the elements titanium (Ti), zirconium (Zr), hafnium (Hf) and rutherfordium (Rf). This group lies in the d-block of the periodic table. The group itself has not acquired a trivial name; it
Periodic table intervals) and the formulation of the first periodic tables. Atomic radii vary in a predictable and explainable manner across the periodic table. For instance, the radii generally decrease along each period of the table, from the alkali metals to the noble gases; and increase down each group. The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom;