State the Modern Periodic Law.

Which of the following statements about the Modern Periodic Table is correct?

Write true or false for the statement: Electronic configuration of hydrogen resembles that of alkaline earth metals.

Write two reasons responsible for the late discovery of noble gases.

Which element has:
$(a)$ two shells,both of which are completely filled with electrons?
$(b)$ the electronic configuration $2, 8, 2$?

$(a)$ State Modern Periodic Law.
$(b)$ Elements $A, B, C$ and $D$ have atomic numbers $1, 8, 11$ and $19$ respectively. Choose the odd element and give reason for your answer.