Question

1. explain and show why ch₃f is a polar molecule, while cf₄ is not.

overall
expectations: c2 and c3
not yet
level 4+
100%
demonstrates the concept of vsepr and polarity with a high degree of effectiveness and accuracy.

• use of correct chemistry terminology
• clear and detailed diagrams/writing
• no errors in solution
• correct and justified conclusion

level 4+
95%
demonstrates the concept of vsepr and polarity, with a high degree of effectiveness and accuracy.

• use of correct chemistry terminology
• clear and detailed diagrams/writing
• correct conclusion
• slight error in solution

level 4-
85%
demonstrates the concept of vsepr and polarity, with a high degree of effectiveness and accuracy.

• use of correct chemistry terminology
• mostly clear and detailed writing/diagrams
• missing one part of q
• minor error in solution
• mostly correct conclusion

level 3
75%
demonstrates the concept of vsepr and polarity, with considerable effectiveness and accuracy.

• use of correct chemistry terminology
• considerable detailed writing/diagrams
• minor errors in solution
• conclusion not justified

level 2
65%
demonstrates the concept of vsepr and polarity, with some effectiveness and accuracy.

• some use of correct chemistry terminology
• some detailed writing/diagrams
• missing more than one part of the q
• few errors in solution

level 1
55%
demonstrates the concept of vsepr and polarity, with limited effectiveness and accuracy.

• limited use of correct chemistry terminology
• major errors in solution
• showed something conceptually related to q

Explanation:

Step1: Analyze VSEPR and bonding in CH₃F

In CH₃F, carbon is the central atom. It has four electron - groups (3 C - H bonds and 1 C - F bond) according to VSEPR. The C - F bond is highly polar due to the large electronegativity difference between C (2.5) and F (4.0). The bond dipoles do not cancel out, resulting in a net dipole moment, making CH₃F a polar molecule.

Step2: Analyze VSEPR and bonding in CF₄

In CF₄, carbon is the central atom with four electron - groups (4 C - F bonds). It has a tetrahedral geometry. Although each C - F bond is polar, the symmetry of the tetrahedral shape causes the bond dipoles to cancel each other out. So, the net dipole moment is zero, and CF₄ is a non - polar molecule.

Answer:

CH₃F is polar because the bond dipoles do not cancel out due to its non - symmetric structure with a highly polar C - F bond. CF₄ is non - polar as the symmetric tetrahedral arrangement of the four polar C - F bonds causes the bond dipoles to cancel, resulting in a net dipole moment of zero.