Read a chemical formula and its ball-and-stick model

Grade 8 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Ari labels a water drop drawing with its formula, H₂O. How many oxygen atoms are in one water molecule?

   • 3 oxygen atoms
   • 1 oxygen atom
   • 2 oxygen atoms
   • 0 oxygen atoms
2. 2.

   Bo blows up a balloon, and the breath inside holds some carbon dioxide, CO₂. How many carbon atoms are in one CO₂ molecule?

   • 3 carbon atoms
   • 0 carbon atoms
   • 2 carbon atoms
   • 1 carbon atom
3. 3.

   On a quiz, Esme meets ammonia, NH₃, a gas with a very strong smell. How many hydrogen atoms are in one NH₃ molecule?

   • 1 hydrogen atom
   • 4 hydrogen atoms
   • 2 hydrogen atoms
   • 3 hydrogen atoms
4. 4.

   One large ball lettered C in the middle, joined by 4 sticks to 4 small balls lettered H. Jun builds methane, CH₄, from clay balls and toothpicks. The model has 1 C ball, 4 H balls and 4 sticks. How many atoms does it show?

   • 4 atoms
   • 5 atoms
   • 2 atoms
   • 8 atoms
5. 5.

   Kira draws an ammonia model: 1 N ball joined by 3 sticks to 3 H balls. It looks a bit like a tiny tripod. How many atoms does it show?

   • 4 atoms
   • 3 atoms
   • 2 atoms
   • 6 atoms
6. 6.

   Luz looks at a hydrogen peroxide model: H–O–O–H, with 3 sticks joining 4 balls in a zigzag. How many atoms does the model show?

   • 4 atoms
   • 3 atoms
   • 2 atoms
   • 7 atoms
7. 7.

   Symbol and name. N nitrogen; Na sodium; Ne neon; Cl chlorine. Milo reads that table salt is NaCl. Which element does the symbol Na stand for?

   • Neon
   • Two elements, N and a
   • Sodium
   • Nitrogen
8. 8.

   Symbol and name. C carbon; Co cobalt; O oxygen. Pia compares two formulas on a card: Co and CO. Which one shows atoms of two different elements?

   • Both show the same two elements
   • Co: carbon and o
   • Neither one
   • CO: carbon and oxygen
9. 9.

   The gas that heats Ren's cooking pot is mostly methane, CH₄. What does one CH₄ molecule hold?

   • 4 hydrogen atoms and no carbon atom
   • 1 carbon atom and 4 hydrogen atoms
   • 2 atoms: 1 carbon, 1 hydrogen
   • 4 carbon atoms and 1 hydrogen atom
10. 10.

    Tala fills a party balloon with air from a pump. Air is mostly nitrogen, N₂. What does one N₂ molecule hold?

    • 2 nitrogen atoms
    • 1 nitrogen atom
    • 3 nitrogen atoms
    • 4 nitrogen atoms