How the periodic table was built and how it is arranged

Answer Key - Grade 10 Science Worksheet - Challenge Me

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

1. 1.

   Chlorine (35.45 u), bromine and iodine (126.904 u) form a triad. What average of chlorine and iodine predicts bromine's mass, to 0.01 u, Bo?

   81.18 u
2. 2.

   Calcium (40.078 u), strontium and barium (137.327 u) form a triad. What average of calcium and barium predicts strontium's mass, to 0.1 u, Esme?

   88.7 u
3. 3.

   A box shows 26, Fe, Iron, 55.845. What is iron's atomic number, Jun?

   • 55.845
   • 26
   • 56
4. 4.

   In the same box, what does 55.845 show, Kira?

   • The year it was found
   • The number of neutrons inside
   • The average atomic mass
5. 5.

   Milo says today's table is ordered by atomic mass. Agree or disagree?

   • Disagree: by atomic number
   • Agree: heavier comes later
   • Agree: Mendeleev's order stayed
6. 6.

   Noah says argon must come after potassium because argon is heavier. Agree or disagree?

   • Disagree: argon has fewer protons
   • Agree: atomic mass sets the order
   • Agree: the table is wrong
7. 7.

   Pia says Mendeleev's gaps were mistakes. Agree or disagree?

   • Disagree: elements filled them
   • Agree: they were removed
   • Agree: gaps mean errors in his work
8. 8.

   How many elements are in period 2, Ren?

   • 2
   • 18
   • 8
9. 9.

   Why does period 4 have 18 elements, Tala?

   • It has 18 groups of shells
   • It has 4 shells of 4 each
   • It adds the 10 d-block elements
10. 10.

    How many elements are in period 6, Zee?

    • 18
    • 72
    • 32