Consider the molecule [ClOF4]+. a) Draw the most accurate Lewis structure [ClOF4]+. Use formal charges to support your drawing. b) Indicate the electron group geometry and molecular geometry of [ClOF4]+. c) Give a 3D drawing of
The Correct Answer and Explanation is:
a) Lewis Structure of [ClOF4]+[ClOF_4]^+[ClOF4]+:
To draw the Lewis structure for [ClOF4]+[ClOF_4]^+[ClOF4]+, follow these steps:
- Count valence electrons:
- Cl: 7 valence electrons
- O: 6 valence electrons
- F × 4: 4 × 7 = 28 valence electrons
- Positive charge (⁺1): subtract 1 electron
- Determine the central atom:
Chlorine (Cl) is less electronegative than O and F, so it will be the central atom. - Arrange atoms:
Place Cl in the center, with one O and four F atoms around it. - Make bonds:
Draw single bonds between Cl and each of the five surrounding atoms (4 F and 1 O). This uses up 5 × 2 = 10 electrons. - Distribute remaining electrons:
You have 40 – 10 = 30 electrons remaining. Distribute these to satisfy the octets of the O and F atoms (each needs 6 more electrons in lone pairs). This uses 5 × 6 = 30 electrons, perfectly filling the valence shells. - Check for formal charges:
Assign formal charges:- F: 7 valence – (6 nonbonding + 1 bonding) = 0
- O: 6 valence – (6 nonbonding + 1 bonding) = −1
- Cl: 7 valence – (0 nonbonding + 5 bonding) = +2
Total = 0 + (4×0) + (−1) + (+2) = +1, which matches the charge on the ion.
✔ Final structure: Cl is bonded to four F atoms and one O atom, all with single bonds. Oxygen bears a −1 formal charge, and Cl bears a +2 formal charge.
b) Electron Group Geometry and Molecular Geometry:
- Electron Groups: Cl has 5 regions of electron density (five bonding pairs).
- Since there are no lone pairs on Cl (assuming the positive charge results from loss of a lone pair), the electron geometry is:
- Trigonal Bipyramidal
- Molecular Geometry: With all positions occupied by atoms, it is also:
- Trigonal Bipyramidal
However, experimentally, the lone pair was removed, and due to different repulsions from F and O, slight distortion occurs, but geometry remains trigonal bipyramidal.
c) 3D Drawing:
Here’s a simplified 3D representation:
rCopyEdit F
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F – Cl – F
/ \
O F
- Two axial fluorines (above and below Cl)
- Two equatorial fluorines and one oxygen in the same plane
- Trigonal bipyramidal shape
Explanation
The molecule [ClOF4]+[ClOF_4]^+[ClOF4]+ is a positively charged species formed when chlorine oxyfluoride gains a positive charge. To understand its structure, we begin by calculating the total number of valence electrons, which amounts to 40. The central atom is chlorine because it is less electronegative than fluorine and oxygen. Around the central chlorine, we place four fluorine atoms and one oxygen atom, each connected via a single bond, consuming 10 electrons.
The remaining 30 electrons are used to complete the octets of the surrounding atoms. When assigning formal charges, we find that oxygen carries a −1 formal charge and chlorine carries a +2 charge, resulting in an overall +1 charge, as expected. This supports the correctness of the Lewis structure.
The central chlorine has five regions of electron density (five bonded atoms and no lone pairs). According to VSEPR (Valence Shell Electron Pair Repulsion) theory, this leads to a trigonal bipyramidal electron geometry. Since all positions are occupied by atoms, the molecular geometry is also trigonal bipyramidal. However, due to different sizes and electronegativities of fluorine and oxygen, there may be slight distortions from ideal bond angles.
In three dimensions, this molecule resembles a trigonal bipyramid: three atoms (including O) are in an equatorial plane, while two fluorines occupy the axial positions. This geometry minimizes electron-pair repulsion and is consistent with the observed structure for similar hypervalent halogen compounds.
