Which one of the following does not increase while moving down the group of the periodic table?

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

''Elements in Periodic Table show periodicity of properties.'' List any four such properties.

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.

$(a)$ Amongst the following elements,identify the ones that would form anions:
$K, O, Na, F, Ca, Cl, Mg$
$(b)$ Write the electronic configuration of the anions identified above.

Write the atomic numbers of two elements $X$ and $Y$ having electronic configurations $2, 8, 2$ and $2, 8, 6$ respectively.