Arrange the following sets of elements according to increasing first ionization energy and according to increasing metallic character. S, Sr, Se, O, Ba, Ca

Explanation:

Given elements:

   S, Sr, Se, O, Ba, Ca

We are to sort the elements:

1. based on their increasing first ionization energy

2. based on their increasing metallic character

First ionization energy is the energy needed to remove the most loosely bonded electron of an atom in the gas phase in the ground state.

  Ionization energy decreases down the group and increases across the period;

 So;

            Ba < Sr < Ca < Se < S < O

Metallic character is the electropositivity of an element. The agility to lose electrons is a measure of an atom's electropostivity;

  Down a group metallic character increases and across a period it reduces.

           O < S < Se < Ca < Sr < Ba