Draw the Lewis structure for SeOBr2 in the window below and then answer the questions that follow. Do not include overall ion charges or formal charges in your drawing. Do not draw double bonds to oxygen atoms unless they are needed for the central atom to obey the octet rule. a. What is the electron-pair geometry for Se in SeOBr2? b. What is the shape (molecular geometry) of SeOBr2? 2. Draw the Lewis structure for SeF6 in the window below and then answer the questions that follow. Do not include overall ion charges or formal charges in your drawing. a. What is the electron-pair geometry for Se in SeF6? b. What is the shape (molecular geometry) of SeF6?
The Correct Answer and Explanation is:
SeOBr2:
- Lewis Structure:
The central atom is selenium (Se), and it is surrounded by two oxygen (O) atoms and two bromine (Br) atoms. Oxygen typically forms two bonds and has two lone pairs, while bromine typically forms one bond and has three lone pairs. To fulfill the octet rule for selenium, the oxygen atoms form single bonds to Se, and one oxygen atom will be double-bonded to Se to ensure that Se has a complete octet. mathematicaCopyEditBr | O - Se - O | Br - Electron-Pair Geometry:
In SeOBr2, the selenium atom has four regions of electron density around it: two single bonds to bromine atoms and one double bond to oxygen, along with one single bond to another oxygen. Therefore, the electron-pair geometry of Se is tetrahedral. - Molecular Geometry:
With four regions of electron density and two lone pairs (from the oxygen atoms), the molecular geometry around selenium is bent or V-shaped. The lone pairs on oxygen will repel the bonding pairs, causing a distortion in the shape.
SeF6:
- Lewis Structure:
Selenium (Se) is the central atom in SeF6, with six fluorine atoms surrounding it. Since fluorine typically forms one bond and has three lone pairs, each fluorine atom will be bonded to the selenium atom with single bonds. Selenium has six bonding pairs of electrons. rCopyEditF | F - Se - F | F - Electron-Pair Geometry:
In SeF6, selenium is surrounded by six fluorine atoms, creating six regions of electron density. The electron-pair geometry around selenium in this molecule is octahedral because six electron pairs arrange themselves to minimize repulsion. - Molecular Geometry:
With six bonding pairs and no lone pairs on selenium, the molecular geometry of SeF6 is also octahedral, as the positions of the fluorine atoms around the selenium atom are symmetrically arranged.
Summary:
- SeOBr2:
- Electron-Pair Geometry: Tetrahedral
- Molecular Geometry: Bent or V-shaped (due to lone pairs on oxygen)
- SeF6:
- Electron-Pair Geometry: Octahedral
- Molecular Geometry: Octahedral (due to no lone pairs on selenium)
