Predict molecular shape

Answer Key - Grade 10 Science Worksheet - Building Confidence

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

1. 1.

   CH₄'s bond angle is 109.5° and H₂O's is 104.48° (NIST). How many degrees smaller is water's, Ari?

   5.02 °
2. 2.

   CH₄'s bond angle is 109.5° and NH₃'s is 106.67° (NIST). How many degrees smaller is ammonia's, Bo?

   2.83 °
3. 3.

   CO₂'s bond angle is 180° and BF₃'s is 120°. How many degrees smaller is BF₃'s, Esme?

   60 °

4. 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

5. 4.

   Using the table, what is CH₄'s bond angle, Kira?

   • 109.5°
   • 120°
   • 90°
6. 5.

   Using the table, why is H₂O bent, Luz?

   • Oxygen is heavy
   • It has just 2 hydrogens
   • It has 2 lone pairs
7. 6.

   What does VSEPR say electron groups do, Milo?

   • Spread as far apart as possible
   • Line up in a row
   • Bunch together on one side of the atom
8. 7.

   How many electron groups does a double bond count as, Noah?

   • Two
   • One
   • Four
9. 8.

   Do lone pairs count as electron groups, Pia?

   • Yes, they take up space too
   • No: bonding pairs are the groups
   • On hydrogen atoms, and nowhere else
10. 9.

    What is the shape of three atoms around a center, flat, at 120°, Ren?

    • Linear
    • Tetrahedral, like CH₄
    • Trigonal planar
11. 10.

    What is the shape of four atoms around a center at 109.5°, Tala?

    • Trigonal planar
    • Bent
    • Tetrahedral