Question

which of the following are non - polar molecules? select all that apply. you may select more than one, one, or none of the options. (note: the central atom of the molecule is underlined)
hcn
bf₃
c₂h₂
nh₃
xef₄

Explanation:

• HCN: The molecule has a linear shape. Carbon forms a triple bond with nitrogen and a single bond with hydrogen. The electronegativity difference between carbon and nitrogen is significant, and the molecule has a net dipole moment, so it is polar.
• BF₃: Boron trifluoride has a trigonal planar geometry. The three B - F bonds are symmetrically arranged. The dipole moments of the B - F bonds cancel each other out, resulting in a non - polar molecule.
• C₂H₂ (acetylene): Acetylene has a linear structure (H - C≡C - H). The C - H bonds are symmetrically placed with respect to the central carbon - carbon triple bond. The dipole moments of the C - H bonds cancel each other, making it a non - polar molecule.
• NH₃: Ammonia has a trigonal pyramidal shape. Nitrogen has a lone pair of electrons. The N - H bonds have a dipole moment, and due to the non - symmetric shape (because of the lone pair), the molecule has a net dipole moment, so it is polar.
• XeF₄: Xenon tetrafluoride has a square planar geometry. The four Xe - F bonds are symmetrically arranged. The dipole moments of the Xe - F bonds cancel each other out, resulting in a non - polar molecule.

Answer:

BF₃, C₂H₂, XeF₄