The molecular geometry of TeF4 (tellurium tetrafluoride) is trigonal bipyramidal.
To understand this geometry, we need to look at the arrangement of the atoms around the central tellurium (Te) atom. Tellurium has six valence electrons. In TeF4, it forms four single bonds with four fluorine (F) atoms, using four of its electrons. This leaves two lone pairs of electrons on the Te atom.
According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, the arrangement that minimizes repulsion among the bond pairs and lone pairs will determine the molecular shape. In the case of TeF4, the two lone pairs are positioned opposite each other to minimize their repulsion, leading to a trigonal bipyramidal arrangement of the four fluorine atoms around the tellurium atom.
In this geometry, three fluorine atoms occupy the equatorial positions, while the remaining fluorine atom occupies an axial position. This gives TeF4 its distinct shape, with bond angles of approximately 120° between the equatorial F-Te-F bonds and 90° between the axial and equatorial bonds.