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

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

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

What is the electronic configuration of sulphur?

Find the atomic number of the element whose electronic configuration is $2, 8, 5$.

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.