What is lanthanoid contraction? Explain its causes and effects.

The lanthanoid contraction relates to

What is lanthanide contraction? Write any two of its consequences.

(i) Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element. (ii) What is lanthanoid contraction? Name an important alloy which contains some of the lanthanoid metals.

What is addition reaction ? Explain its reaction mechanism with an example.

What is biomagnification ? Explain its ill effect.