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?

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

   Why does CH₄ have the full tetrahedral angle, Luz?

   • It has double bonds
   • It has no lone pairs
   • Carbon is flat
6. 6.

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

   • Trigonal planar
   • Bent
   • Linear
7. 7.

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

   • Tetrahedral
   • Trigonal pyramidal
   • Trigonal planar
8. 8.

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

   • Bent
   • Tetrahedral
   • Linear

9. 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

10. 9.

    Using the table, what is BF₃'s shape, Ren?

    • Trigonal pyramidal
    • Trigonal planar
    • Bent
11. 10.

    Using the table, what happens to the angle as lone pairs rise from 0 to 2, Zee?

    • It stays at 109.5°
    • It grows
    • It shrinks