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

Three elements $B, Si$ and $Ge$ are:

State whether the following statements are true or false: In the Modern Periodic Table,a zig-zag line separates metals from non-metals. The borderline elements—boron,silicon,germanium,arsenic,antimony,tellurium,and polonium—are intermediate in properties and are called metalloids or semimetals.

Where would you locate the element with electronic configuration $2, 8$ in the Modern Periodic Table?

The scientist who showed that the atomic number of an element is a more fundamental property than its atomic mass is:

How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?