Which sample is a mixture?
naci(l) or naci(aq)

can you explain why?

in  chemistry, a  mixture  is a  material  made up of two or more different  substances  which are physically combined.[1]a mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of  solutions,  suspension  and  colloids.[2][3]

mixtures are one product of mechanically blending or mixing chemical substances such as  elements  and  compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup.[4]  despite the fact that there are no chemical changes to its constituents, the physical properties of a mixture, such as its  melting point, may differ from those of the components. some mixtures can be  separated  into their components by using physical (mechanical or thermal) means.  azeotropes  are 

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.