Final answer:
The shape of the SeH₂ molecule is bent due to its two bonding pairs and two lone pairs, according to VSEPR theory. The presence of lone pairs forces the hydrogen atoms closer together, forming a V-shape with a net dipole moment.
Step-by-step explanation:
The shape of the SeH₂ molecule, also known as hydrogen selenide, can be determined by using Lewis Dot structures and VSEPR theory. First, we recognize that selenium (Se) is the central atom with six valence electrons. The Lewis Dot structure for SeH₂ will have Se in the center with two hydrogen atoms bonded to it, each contributing one electron for the single bonds. This results in selenium having two bonding pairs and two lone pairs.
According to VSEPR theory, the four electron pairs around the selenium atom will arrange themselves to be as far apart as possible, which means they will adopt a tetrahedral arrangement. However, because there are two lone pairs and only two bonding pairs, the shape of the molecule will be bent (angular), similar to a V-shape, rather than a perfect tetrahedron. The presence of lone pairs repels the bonding pairs closer together, causing the molecule to bend.
The bond dipoles in SeH₂ do not cancel each other out due to its bent molecular geometry, which means that the molecule has a net dipole moment, making it polar.