are these molecules polar or nonpolar?

1. [PO4] 3-

2. [NO2]-

3. SO3

See your post below.

To determine if a molecule is polar or nonpolar, you need to consider its molecular geometry and the polarity of its individual bonds. Here's how you can analyze each molecule to determine their polarity:

1. [PO4]3-:
To determine the polarity of this molecule, you need to examine the geometry around the central atom (P) and the electronegativities of the surrounding atoms. In this case, the central atom (P) has four oxygen atoms bonded to it. The molecule has a tetrahedral shape, and all the atoms surrounding the central atom are the same (oxygen). Since oxygen is highly electronegative, the oxygen atoms pull the electron pairs towards them, resulting in a polar molecule.

2. [NO2]-
For this molecule, the central atom is nitrogen (N), and it is bonded to two oxygen (O) atoms. The geometry around the central atom is trigonal planar. Nitrogen is more electronegative than oxygen, so the electronegativity difference between the atoms causes the bonds to be polar. Additionally, the lone pair on nitrogen contributes to the overall polarity of the molecule. Thus, [NO2]- is polar.

3. SO3:
In this molecule, sulfur (S) is the central atom, and it is bonded to three oxygen (O) atoms. The geometry around the central atom is trigonal planar. Oxygen is more electronegative than sulfur, so the bonds in the molecule are polar. However, due to the symmetry of the molecule, the polarities of the bonds cancel out each other, resulting in a nonpolar molecule.

To summarize:

1. [PO4]3-: Polar
2. [NO2]-: Polar
3. SO3: Nonpolar