Which of the following is the valence shell for the elements of second period of the modern periodic table?

Where would you locate the element with electronic configuration 2, 8 in the modern periodic table?

An element which is an essential constituent of all organic compouds belongs to following group of modern periodic table:

The element which has the maximum number of valence electrons is:

The correct increasing order of the atomic radii of the elements oxygen, fluorine and nitrogen is: