How the periodic table was built and how it is arranged

Answer Key - Grade 10 Science Worksheet - Building Confidence

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

1. 1.

   Mendeleev published his table in 1869, and gallium was found in 1875. How many years passed, Ari?

   6 years
2. 2.

   Mendeleev published his table in 1869, and germanium was found in 1886. How many years passed, Bo?

   17 years
3. 3.

   Mendeleev published his table in 1869, and scandium was found in 1879. How many years passed, Esme?

   10 years

4. Read this first

   Mendeleev's 1871 predictions and the elements found later (Mendeleev 1871; modern values from PubChem)

   predicted element	found as	year found	atomic mass (predicted / found)	density in g/cm³ (predicted / found)
   eka-aluminium	gallium	1875	68 / 69.723	6.0 / 5.91
   eka-boron	scandium	1879	44 / 44.956	not predicted
   eka-silicon	germanium	1886	72 / 72.63	5.5 / 5.323

5. 4.

   Using the table, which element did Mendeleev call eka-silicon, Jun?

   • Gallium
   • Germanium
   • Scandium
6. 5.

   Using the table, which predicted element was found first, Kira?

   • Gallium, in 1875
   • Germanium, in 1886
   • Scandium, in 1879
7. 6.

   Using the table, how close was Mendeleev's mass for germanium, Luz?

   • Far off: 44 against 72.63
   • Far off: 68 against 72.63
   • Close: 72 against 72.63
8. 7.

   How did Mendeleev arrange the elements in 1869, Milo?

   • In alphabetical order
   • By mass, grouped by properties
   • By atomic number
9. 8.

   What did Mendeleev do when no known element fit a spot, Noah?

   • Moved the pattern
   • Left a gap for one
   • Dropped the column
10. 9.

    When did Mendeleev publish his periodic table, Pia?

    • 1869
    • 1808
    • 1913
11. 10.

    How many groups does the modern periodic table have, Zee?

    • 18
    • 8
    • 7