The molar mass of O2 is 32g/mol. So the mol amount of these O2 is 56/32=2 mol. STP stands for the standard temperature and pressure which means the temperature is 0 ℃ and pressure is 100 kPa. And the molar volume of gas is 22.7 L/mol under STP. So the answer is 22.7*2=45.4 L
Element atomic number position
Ba 56 group 2, period 6
Ca 12 group 2, period 3
S 16 group 16, period 3
Si `14 group 14, period 3
Now, you need to know the properties of the different type of elements and the tendencies on the periodic table.
The metallic elements are, those placed on the left side of the periodic table, are the ones that release an electron more easily, so they will requiere less energy to give it up when forming chemical bonds.
The higher the metallic character the less the energy need to give up an electron.
The metallic character grows as the group number decreases (goes to the left) period increases (goes downward), so among the elements considered, Barium will require the least amount of energy to give un an electron when forming chemical bonds.
