The shape of Cl2 (chlorine gas) is linear. This is because Cl2 consists of two chlorine atoms bonded together with a single covalent bond.
In terms of molecular geometry, Cl2 does not have any lone pairs of electrons on the central atom (in this case, there is no central atom, as there are only two atoms). The bonding electrons are shared equally between the two chlorine atoms. Therefore, the molecule adopts a straight line configuration, which is characteristic of diatomic molecules.
Moreover, since both atoms are identical, there is no difference in electronegativity to create a dipole moment, reinforcing the linear shape of the molecule.