What is the most common oxidation state of lanthanides?

What is the common oxidation state of scandium? (At. No. of Sc = 21)

Which compound is used in Ultra-violet calibration?

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

What is the oxidation state exhibited by actinium?

Which of the following has the highest density?

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

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