Predict molecular shape

Answer Key - Grade 10 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   For n electron groups spread as far apart as possible, the angle is cos⁻¹(−1 ÷ (n − 1)). What is it for n = 2, to 0.01°, Ari?

   180 °
2. 2.

   For n electron groups spread as far apart as possible, the angle is cos⁻¹(−1 ÷ (n − 1)). What is it for n = 3, to 0.01°, Bo?

   120 °
3. 3.

   For n electron groups spread as far apart as possible, the angle is cos⁻¹(−1 ÷ (n − 1)). What is it for n = 4, to 0.01°, Esme?

   109.47 °
4. 4.

   Why is NH₃'s angle (106.67°) smaller than CH₄'s (109.5°), Jun?

   • Nitrogen is bigger than carbon
   • It has more hydrogens
   • Its lone pair pushes the bonds closer
5. 5.

   Why is H₂O's angle smaller than NH₃'s, Kira?

   • It has fewer bonds to fill
   • It has two lone pairs
   • Oxygen has no lone pairs
6. 6.

   Why does CH₄ have the full tetrahedral angle, Luz?

   • It has no lone pairs
   • It has double bonds
   • Carbon is flat
7. 7.

   A central atom has two bonds and two lone pairs. What shape is the molecule, Milo?

   • Trigonal planar
   • Linear
   • Bent
8. 8.

   A central atom has three bonds and one lone pair. What shape is the molecule, Noah?

   • Trigonal planar
   • Trigonal pyramidal
   • Tetrahedral
9. 9.

   A central atom has two double bonds and no lone pairs. What shape is the molecule, Pia?

   • Linear
   • Tetrahedral
   • Bent

10. Read this first

    Molecule sketches with shapes and bond angles (VSEPR; NH₃ and H₂O angles from NIST CCCBDB)

    molecule	electron groups on the center	lone pairs on the center	shape	bond angle (°)
    CO₂	2	0	linear	180
    BF₃	3	0	trigonal planar	120
    CH₄	4	0	tetrahedral	109.5
    NH₃	4	1	trigonal pyramidal	106.67
    H₂O	4	2	bent	104.48

11. 10.

    Using the table, which three molecules have 4 electron groups on the center, Tala?

    • CH₄, NH₃ and H₂O
    • CO₂, BF₃ and CH₄
    • BF₃, NH₃ and H₂O