Draw the Lewis structure of ClBr: showing all lone pairs. Identify the molecular geometry of ClBr3
The correct answer and explanation is :
To draw the Lewis structure of ClBr3 (Chlorine tribromide), we follow these steps:
- Count the valence electrons:
Chlorine (Cl) is in group 17, so it has 7 valence electrons.
Bromine (Br) is also in group 17, so each bromine atom has 7 valence electrons.
Since there are three bromine atoms, the total number of valence electrons is:
[
(7 \times 1) + (7 \times 3) = 7 + 21 = 28 \text{ valence electrons}.
] - Determine the central atom:
Chlorine (Cl) is the least electronegative atom, so it will be the central atom in this molecule. - Draw the skeletal structure:
Chlorine (Cl) will be connected to each of the three bromine (Br) atoms by single bonds. Each single bond consists of two electrons. This will use 6 electrons, leaving 22 electrons to be placed as lone pairs. - Distribute the remaining electrons:
Each bromine atom will be assigned 3 lone pairs of electrons (6 electrons), which use up 18 electrons. The remaining 4 electrons will be placed as lone pairs on the chlorine atom. - Check the octet rule:
Chlorine (Cl) can have more than 8 electrons in its valence shell since it is in period 3 and can accommodate up to 12 electrons. So, placing the remaining lone pairs on chlorine is acceptable.
Lewis Structure of ClBr3:
The structure is as follows:
- Chlorine (Cl) is the central atom, bonded to three bromine (Br) atoms with single bonds.
- Each bromine (Br) atom has three lone pairs of electrons.
- Chlorine (Cl) has two lone pairs of electrons.
Molecular Geometry of ClBr3:
The molecular geometry of ClBr3 is T-shaped. This is due to the following reasoning:
- Electron pairs around Cl: Chlorine has five regions of electron density (three single bonds with bromine and two lone pairs).
- Electron repulsion: According to the VSEPR (Valence Shell Electron Pair Repulsion) theory, these regions of electron density will arrange themselves as far apart as possible. The lone pairs will occupy positions that minimize repulsion, leading to a T-shaped structure.
Explanation:
The electron pairs in the ClBr3 molecule arrange themselves into a trigonal bipyramidal electron geometry with the three bromine atoms occupying the equatorial positions and the two lone pairs occupying the axial positions. The lone pairs exert a greater repulsion on the bonding pairs, which distorts the molecule into a T-shaped geometry. The bond angles in a T-shaped molecule are typically around 90° and 180°, but may be slightly compressed due to the lone pair repulsion.
Thus, the molecular geometry of ClBr3 is T-shaped with a bond angle of approximately 90° between the bromine atoms in the equatorial positions.