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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 6a

The orbital diagram that follows presents the final step in the formation of hybrid orbitals by a silicon atom. (a) Which of the following best describes what took place before the step pictured in the diagram: (i) Two 3p electrons became unpaired, (ii) An electron was promoted from the 2p orbital to the 3s orbital, or (iii) An electron was promoted from the 3s orbital to the 3p orbital?
Orbital diagram showing hybridization of silicon with unpaired 3p electrons.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hybridization

Hybridization is the process by which atomic orbitals mix to form new hybrid orbitals, which are used to describe the bonding in molecules. In the case of silicon, the 3s and 3p orbitals combine to create four equivalent sp3 hybrid orbitals, allowing for the formation of four covalent bonds. Understanding hybridization is crucial for predicting molecular geometry and bonding properties.
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Electron Promotion

Electron promotion refers to the process where an electron from a lower energy orbital is excited to a higher energy orbital. This is often necessary for hybridization to occur, as it allows for the formation of unpaired electrons in the orbitals involved in bonding. In silicon, promoting an electron from the 3s to the 3p orbital enables the formation of the required unpaired electrons for hybridization.
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Orbital Diagrams

Orbital diagrams visually represent the distribution of electrons in an atom's orbitals. Each box represents an orbital, and arrows indicate the presence of electrons, with their spins. These diagrams help in understanding the electron configuration and the process of hybridization, as they illustrate how electrons are arranged before and after hybridization occurs.
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