Question

in each of the molecules drawn below one chemical bond is colored red. decide whether this bond is likely to be polar or not. if the bond is likely to be polar, write down the chemical symbol for the atom which will have more negative charge.
:cl — f:
the highlighted bond is polar and the more negative atom is
the highlighted bond is nonpolar.
h
h — n — h
the highlighted bond is polar and the more negative atom is
the highlighted bond is nonpolar.
h — br:
the highlighted bond is polar and the more negative atom is
the highlighted bond is nonpolar.

Explanation:

Step1: Recall electronegativity concept

A polar bond forms when there is a significant electronegativity difference between two atoms. The more electronegative atom attracts the bonding - electrons more and has a partial negative charge.

Step2: Analyze Cl - F bond

The electronegativity of F is 3.98 and of Cl is 3.16. Since there is an electronegativity difference ($\Delta\chi=3.98 - 3.16=0.82$), the Cl - F bond is polar. Fluorine is more electronegative, so the more negative atom is F.

Step3: Analyze N - H bond

The electronegativity of N is 3.04 and of H is 2.20. The electronegativity difference ($\Delta\chi = 3.04-2.20 = 0.84$), so the N - H bond is polar. Nitrogen is more electronegative, so the more negative atom is N.

Step4: Analyze H - Br bond

The electronegativity of Br is 2.96 and of H is 2.20. The electronegativity difference ($\Delta\chi=2.96 - 2.20=0.76$), so the H - Br bond is polar. Bromine is more electronegative, so the more negative atom is Br.

Answer:

1. The highlighted bond is polar and the more negative atom is F
2. The highlighted bond is polar and the more negative atom is N
3. The highlighted bond is polar and the more negative atom is Br