State a reason why most chemicals are stored in glass or plastic containers rather than metallic ones

Because if they were stored in metallic containers...the chemicals will react with the metal,only to give a new product...hence making the chemical not usable for its purpose.

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.