Why does it take less energy to boil water on a mountain then at sea level

When pressure decreases, the boiling point also decreases. There is less pressure on a mountain then there is at sea level, so the water's boiling point should decrease on the top of a mountain. Because the boiling point decreases, it would take less energy(heat) to make the water boil.

I hope this helps. :)

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.