Which of the following element has the highest ionisation enthalpy?

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

The decrease in atomic size of the d-block elements in a series is small after midway.

Which of the following statements is incorrect?

Silver bromide is used in photography.

Why is there an increase in the atomic radius of transition elements at the end of the period?

Which is the most stable oxidation state of actinoids?

Which of the following lanthanide ions do not exhibit color?