To determine the molecular shape of selenium tetrachloride (SeCl4), we need to consider its molecular geometry, which can be understood using the VSEPR (Valence Shell Electron Pair Repulsion) theory.
Selenium (Se) is the central atom in SeCl4 and has six valence electrons. In this compound, Se is bonded to four chlorine (Cl) atoms. This creates four bonding pairs of electrons that are involved in bonding with the Cl atoms.
However, selenium also has two lone pairs of electrons that are not involved in bonding. To visualize the shape, we start by determining the electron pair geometry. With four bonding pairs and two lone pairs, the arrangement of electron pairs around the selenium atom corresponds to an octahedral electron geometry.
Now, when we take into account the lone pairs, which occupy more space than the bonding pairs, the molecular shape is affected. The presence of the two lone pairs pushes the bonding pairs down, resulting in a square planar molecular shape.
In summary, the molecular shape of SeCl4 is square planar due to the arrangement of its four bonding pairs and two lone pairs according to the VSEPR theory.