Question

Select all the molecules and/or ions containing double bonds that have trigonal planar shapes.

A. NO₂⁻
B. SO₃
C. NO₃⁻

Answer 1

The molecules and/or ions containing double bonds that have trigonal planar shapes are B. SO₃.

Step-by-step explanation:

SO₃ (Sulfur trioxide) exhibits trigonal planar geometry. This structure arises due to the arrangement of atoms around the sulfur atom, which forms three double bonds with oxygen atoms. The sulfur atom utilizes its three sp² hybrid orbitals to form sigma bonds with the oxygen atoms. This molecular arrangement satisfies the octet rule for each atom, providing stability to the molecule.

The Lewis structure of SO₃ depicts three double bonds between sulfur and oxygen atoms. Each oxygen atom shares a double bond with sulfur, and there are no lone pairs on the central sulfur atom. According to valence shell electron pair repulsion (VSEPR) theory, the repulsion between the bonding pairs and lone pairs determines the molecular geometry. In the case of SO₃, the repulsion between the three bonding pairs leads to a trigonal planar shape, with an angle of approximately 120 degrees between each of the sulfur-oxygen bonds.

The trigonal planar geometry of SO₃ is evident when considering its molecular shape, where the sulfur atom sits at the center, surrounded by three oxygen atoms forming a planar arrangement. This molecular shape is a result of the arrangement of bonding electron pairs, which maximize their separation to minimize repulsion, thereby adopting a trigonal planar geometry in three-dimensional space. Thus, among the given options, only SO₃ meets the criteria of having double bonds and a trigonal planar shape.

Answer 2

NO₂⁻ and NO₃⁻ contain double bonds and have trigonal planar shapes. So, the correct options are A. NO₂⁻ and C. NO₃⁻.

Step-by-step explanation:

The molecules and ions in question contain double bonds and exhibit trigonal planar shapes due to their molecular geometry. NO₂⁻ possesses a double bond between nitrogen and one oxygen atom, with a lone pair on nitrogen, resulting in a trigonal planar shape. Similarly, NO₃⁻ features a double bond between nitrogen and one oxygen atom, along with two other oxygen atoms bonded through single bonds, leading to a trigonal planar configuration due to the arrangement of its atoms. SO₃, however, does not contain double bonds; it comprises three double bonds between sulfur and oxygen atoms but adopts a trigonal planar shape based on its bonding and lone pair arrangement.

In both NO₂⁻ and NO₃⁻, the presence of a double bond contributes to the planar shape, as it influences the spatial arrangement of atoms and lone pairs around the central atom. The double bonds within these molecules cause a repulsion that arranges the surrounding atoms in a trigonal planar manner. Meanwhile, SO₃ contains three double bonds, yet its trigonal planar shape arises due to the arrangement of the bonding and non-bonding electron pairs around the sulfur atom, creating a symmetrical, planar structure. Therefore, while all three molecules exhibit a trigonal planar shape, only NO₂⁻ and NO₃⁻ contain double bonds, influencing their overall geometry.

So, the correct options are A. NO₂⁻ and C. NO₃⁻.