For the molecules SiH4 and CSe2, give
total number of valence electrons present
Lewis structure
electron and molecular geometry
bond angle
polarity of molecule
The Correct Answer and Explanation is :
Let’s analyze the molecules SiH₄ (silane) and CSe₂ (carbon diselenide) in terms of their valence electrons, Lewis structures, electron and molecular geometries, bond angles, and polarity.
SiH₄ (Silane):
- Valence Electrons: – Silicon (Si): 4 valence electrons – Hydrogen (H): 1 valence electron per atom × 4 atoms = 4 valence electrons – Total: 4 (Si) + 4 (H) = 8 valence electrons
- Lewis Structure: – Silicon is the central atom, forming single bonds with four hydrogen atoms. – Each Si-H bond involves two electrons, utilizing all 8 valence electrons.
- Electron and Molecular Geometry: – Electron Geometry: Tetrahedral, as there are four bonding pairs around the central silicon atom. – Molecular Geometry: Tetrahedral, since there are no lone pairs on silicon.
- Bond Angle: – Approximately 109.5°, characteristic of a tetrahedral arrangement.
- Polarity: – The Si-H bonds are slightly polar due to the difference in electronegativity between Si and H. – However, the symmetrical tetrahedral shape causes the individual dipoles to cancel out, resulting in a nonpolar molecule.
CSe₂ (Carbon Diselenide): - Valence Electrons: – Carbon (C): 4 valence electrons – Selenium (Se): 6 valence electrons per atom × 2 atoms = 12 valence electrons – Total: 4 (C) + 12 (Se) = 16 valence electrons
- Lewis Structure: – Carbon is the central atom, forming double bonds with two selenium atoms. – Each double bond uses 4 electrons, totaling 8 electrons. – The remaining 8 electrons are placed as lone pairs on the selenium atoms.
- Electron and Molecular Geometry: – Electron Geometry: Linear, as there are two regions of electron density (the two double bonds) around the central carbon atom. – Molecular Geometry: Linear, since there are no lone pairs on carbon.
- Bond Angle: – 180°, characteristic of a linear arrangement.
- Polarity: – The C=Se bonds are polar due to the difference in electronegativity between carbon and selenium. – The linear shape causes the dipoles to cancel out, resulting in a nonpolar molecule.
For a visual explanation of SiH₄’s molecular geometry and bond angles, you might find the following video helpful:
videoSiH₄ Molecular Geometry, Bond Anglesturn0search0