Question

Silicon is immediately under carbon in the Periodic Table. Predict the geometry of silane, \(\mathrm{SiH}_{4}\).

Short answer

Answer: The predicted geometry of silane (SiH4) is tetrahedral with bond angles of about 109.5° between the Si-H bonds.

Step-by-step solution

(Step 1: Determine the number of valence electrons)

(Silicon has four valence electrons, and each hydrogen atom has one valence electron. Therefore, the total number of valence electrons in silane is 4 (from Silicon) + 4 x 1 (from 4 Hydrogen atoms) = 8 valence electrons.)

(Step 2: Draw the Lewis structure of SiH4)

(To draw the Lewis structure of SiH4, we start by placing Silicon in the center and surrounding it with four Hydrogen atoms. We then connect each Hydrogen atom to Silicon with a single bond, using up 4 pairs or 8 valence electrons. The final Lewis structure for SiH4 is: ``` H | H--Si--H | H ``` )

(Step 3: Identify the electron groups around the central atom)

(In the Lewis structure of SiH4, there are four electron groups around the central Silicon atom, each associated with a single bond to a Hydrogen atom. Thus, we have four bonding electron groups.)

(Step 4: Predict the geometry of SiH4 using the VSEPR theory)

(Based on the VSEPR theory, a molecule with four electron groups around the central atom will adopt a tetrahedral geometry to minimize the repulsive forces between these electron groups. Therefore, we can predict that the geometry of silane (SiH4) is tetrahedral, with the bond angles of about 109.5° between the Si-H bonds.)