Molecular formula: SbCl5 The following is needed: Number of valence electrons: AXmEn notation: Electron pair arrangement: Molecular geometry:
The correct answer and explanation is:
Molecular formula: SbCl₅
Number of valence electrons: 40
AXmEn notation: AX₅E₀
Electron pair arrangement: Trigonal bipyramidal
Molecular geometry: Trigonal bipyramidal
Antimony pentachloride (SbCl₅) is a compound consisting of one antimony atom and five chlorine atoms. To determine its structure, it is important to count the number of valence electrons. Antimony (Sb) is in group 15 of the periodic table, so it has 5 valence electrons. Each chlorine atom contributes 7 valence electrons, and since there are 5 chlorine atoms, they contribute a total of 35 electrons. Therefore, the total number of valence electrons in SbCl₅ is 5 (from Sb) + 35 (from Cl) = 40 valence electrons.
In AXmEn notation, “A” represents the central atom (Sb), “X” represents bonded atoms (five Cl atoms), and “E” represents lone pairs on the central atom. Since all five valence orbitals on Sb are used for bonding and there are no lone pairs remaining on the central atom, the notation becomes AX₅E₀.
With five bonding pairs and no lone pairs, the electron pair arrangement is trigonal bipyramidal, which means three chlorine atoms are arranged in an equatorial plane, 120 degrees apart, while the other two are positioned axially, 90 degrees from the equatorial atoms.
Because there are no lone pairs on the central atom, the molecular geometry is the same as the electron pair arrangement: trigonal bipyramidal. This geometry minimizes electron-pair repulsion according to the VSEPR (Valence Shell Electron Pair Repulsion) theory. The structure allows the five chlorine atoms to be as far apart as possible, reducing repulsion and stabilizing the molecule. This makes SbCl₅ a classic example of a molecule with five bonding domains and no lone pairs, resulting in a symmetric and well-defined three-dimensional shape.