NSS_25_bond_polarity_2425_ans.pdf

A non‑polar covalent bond involves equal sharing of electrons between atoms with the same or very similar electronegativity. Example: H2 (or O2, N2). Non‑polar: bonding electrons are shared equally.

BF3 is trigonal planar with three equal B–F bond dipoles symmetrically arranged; the dipoles cancel each other, so the molecule has no net dipole and is non‑polar.

CCl4 is tetrahedral and the four equal C–Cl bond dipoles are symmetrically arranged and cancel, resulting in net dipole = 0 → non‑polar.

H2O is V‑shaped (bent); the two O–H bond dipoles do not cancel and add to produce a net dipole moment directed toward oxygen, so H2O is polar.

NH3 is trigonal pyramidal with three N–H bond dipoles and a lone pair on N; the arrangement is asymmetric, so the bond dipoles do not cancel and the molecule has a net dipole → polar.

Strategy: (1) Draw the molecule's 3D shape; (2) Show the bond dipole(s) for any polar bonds; (3) Vector‑add the dipoles to find the net dipole. If net = 0 → non‑polar; if net ≠ 0 → polar.

BeCl2 is linear (Cl–Be–Cl). The two equal bond dipoles point in opposite directions and cancel, so BeCl2 is non‑polar (net dipole = 0).

SF6 is octahedral with six equal S–F bond dipoles symmetrically arranged; the dipoles cancel, so SF6 is non‑polar (net dipole = 0).

Bring a charged rod near a thin jet of liquid. Polar liquids (e.g., water) are attracted to the rod because molecules reorient so opposite partial charges face the rod; non‑polar liquids (e.g., CCl4) are not attracted. Use this to distinguish polar vs non‑polar liquids.

In an electric field, polar molecules (with net dipole) reorient to align with the field (order increases). Non‑polar molecules remain largely random and are not significantly affected.

Electronegativity increases across a period (left→right) and decreases down a group. The most electronegative element is fluorine (F).

Compare the electronegativity difference between two bonded atoms: if the values are identical or very similar → non‑polar; if different → polar. Generally, larger differences mean more polar bonds.

A dipole moment is a vector measure of bond polarity (magnitude and direction). It is shown as an arrow with a crossed tail (+→) pointing toward the partial negative end; the crossed tail marks the partial positive end.

The more polar the bond (larger electronegativity difference), the larger the dipole moment. Dipole moment quantifies how strongly electrons are displaced in a bond.

Sum the individual bond dipole vectors to get the net dipole moment. If net dipole = 0 → molecule is non‑polar; if net dipole ≠ 0 → molecule is polar.

CO2 is linear with two equal C=O bond dipoles pointing in opposite directions. The bond dipoles cancel, giving a net dipole = 0, so CO2 is non‑polar.

A covalent bond is formed when electrons are shared between two atoms and arises from the electrostatic attraction between the positively charged nuclei and the negatively charged bonding electrons. Covalent bond = shared electrons between atoms.

A polar covalent bond has unequal sharing of electrons due to a difference in electronegativity, producing partial charges (δ+ and δ−). Example: HCl (Cl is δ−, H is δ+).