A known number of moles of gas is placed in the flexible container below What will happen it some of the gas is removed from the container while
the pressure and temperature are kept constant?
The volume will increase
The volume will decrease
The volume will stay the same

the answer is barium and copper bromide

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.