For F2, describe the central atom and number of unshared pairs of electrons in the molecule, if any.
Atoms of elements combine with each other to form molecules so that the number of electrons in the outermost shell of each atom is equal to that of the nearest noble gas. This can be 2, 8, 18... depending on the number of electronic configuration of the elements.
Fluorine has an electronic configuration of 1s22s22p5with 7 electrons in the outermost shell. It has to gain 1 electron to achieve a stable outermost shell electron configuration of 2s2 2p6. This is done in the F2 molecule by each fluorine atom sharing 1 electron with the other.
This results in a stable electron configuration for each of the atoms. After the bond is formed each fluorine atom has 6 electrons that are not shared.
Now in F2 there are 2 F atom, so there wont be any central atom.
now the electron configuration of F is 1s2 2s2 2p5. (7 electron in outermost shell)
so it requries 1 more electron to attain stable state (ns2 np6-octet rule).
So it shared one of its electron with another F molecule so that both of them have 8 electron in their valance shell
F-F or F2
So there is a single bond between F2 and 3 lone pair (6 electrons) each.
A Fluorine atom forms a covalent bond with another Fluorine atom to attain a stable electronic configuration hence the molecule formed has no central atom
Electronic configuration of Fluorine is (2,7) which means it has 7 electrons in its valence shell and to attain stable electronic configuration it attains the electronic configuration of Neon (2,8) by gaining one electron
It forms a single covalent bond F-F it has 3 lone pairs