Which of the following statements is incorrect?

Which of the following is not a very hard metal?

Which of the following element belongs to the first transition series of the periodic table?

What is the most common oxidation state of lanthanides?

Why do transition elements form alloys so easily?

Which is the most stable oxidation state of actinoids?

The main factor for the cause of lanthanide contraction is poorer shielding of 5d electrons by 4f electrons.

All actinoids are diamagnetic in nature.