What is the common oxidation state shown by Lanthanoids? Mention any one consequence of Lanthanoid contraction. 

Explanation

`+3` is the common oxidation state shown by lanthannoids.
Consequence
i) 4d and 5d sereis transaction elements have almost identical size/radii.
ii) `Zr - 4F//M_(0) - W` occur together in nature i.e., Due to lanthanoid contraction the atomic radii of `Zr" (160 pm)"` and `"HF (159 pm)"` is almost same so they occur together. Hence it is difficult to separate them.