2. What makes up the space between atoms?

The nucleus makes up a tiny proportion of the space occupied by an atom, while the electrons make up the rest. According to quantum electrodynamics, the space is filled by an electron field around the nucleus which neutralizes its charge and fills the space defining the atom size.

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.