Magnesium hydride (MgH₂) does not form discrete molecules like water (H₂O) or methane (CH₄). Instead, it forms a ionic crystal lattice.

Here's why:

* Ionic Bonding: Magnesium (Mg) is a metal and readily loses two electrons to form a +2 cation (Mg²⁺). Hydrogen (H) is a nonmetal and readily gains one electron to form a -1 anion (H⁻). The strong electrostatic attraction between these oppositely charged ions forms the ionic bond.

* Crystal Lattice: In magnesium hydride, the Mg²⁺ and H⁻ ions arrange themselves in a repeating, three-dimensional structure called a crystal lattice. This structure maximizes the attractive forces between the ions while minimizing the repulsive forces.

Therefore, it's incorrect to talk about the "molecular shape" of magnesium hydride. Instead, we describe the crystal structure of the ionic compound.