Classification of Elements and Periodicity in Properties

Which of the following elements has the most negative electron gain enthalpy?...

The general valence shell electronic configuration of d-block elements is:...

Which of the following oxide is amphoteric in nature?...

Why is the first ionization enthalpy of Nitrogen ($N$) higher than that of Oxygen ($O$)?...

Lithium shows a diagonal relationship with which of the following elements?...