Question

Consider the bonding in an \(\mathrm{MgH}_{2}\) molecule. (a) Draw a Lewis structure for the molecule, and predict its molecular geometry. (b) What hybridization scheme is used in \(\mathrm{MgH}_{2} ?\) (c) Sketch one of the two-electron bonds between an \(\mathrm{Mg}\) hybrid orbital and an \(\mathrm{H} 1 \mathrm{~s}\) atomic orbital.

Short answer

The MgH₂ molecule has a linear molecular geometry with an sp hybridization scheme. The Lewis structure is: ``` H | Mg | H ``` In the bond between an Mg hybrid orbital and an H 1s atomic orbital, there is an overlap forming a σ (sigma) bond: ``` Mg(sp hybrid orbital) - H(1s atomic orbital) ```

Step-by-step solution

Draw the Lewis Structure and Predict Molecular Geometry

We begin by drawing the Lewis structure of the MgH₂ molecule. 1. Count the total number of valence electrons in the molecule. Magnesium (Mg) has 2 valence electrons and each hydrogen (H) atom has 1 valence electron, for a total of 4 valence electrons. 2. Arrange the atoms in the molecule, placing the least electronegative atom (Mg) in the center. 3. Distribute the valence electrons, forming single bonds first (2 electrons/bond). 4. If any electrons are left, place them as lone pairs. Considering these steps, the Lewis structure for MgH₂ is: ``` H | Mg | H ``` There are no lone pairs on the central Mg atom and it is bonded to two H atoms. Based on the VSEPR (valence shell electron pair repulsion) theory, the molecular geometry of MgH₂ is linear.

Determine the Hybridization Scheme

To determine the hybridization scheme, we need to look at the number of electron regions around the central atom (Mg). In this case, we have two such regions, as Mg is bonded to two H atoms. According to the hybridization theory, when there are two electron regions, the hybridization scheme used is sp. Therefore, the hybridization scheme for MgH₂ is sp.

Sketch the Bond between an Mg Hybrid Orbital and an H 1s Atomic Orbital

To sketch the bond between an Mg hybrid orbital and an H 1s atomic orbital, follow these steps: 1. Draw the central Mg atom with its sp hybrid orbitals. It will have two such orbitals, each directed linearly, one towards one hydrogen atom and the other one towards the other hydrogen atom. 2. Draw the two H atoms with their 1s atomic orbitals. 3. Show the overlap between an Mg sp hybrid orbital and an H 1s atomic orbital, forming the σ (sigma) bond. Here is the sketch of an Mg hybrid orbital overlapping with an H 1s atomic orbital (single bond). ``` Mg(sp hybrid orbital) - H(1s atomic orbital) ```