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Natural Science - Year II

Unit 39: Search for the Elements

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Science Web Assignment for Unit 39

This Unit's Homework Page History Lecture Science Lecture Lab Parents' Notes

Science Lecture for Unit 39: Modern Chemistry and the Periodic Table

For Class

The Periodic Table

Units of measurement

Among of the tools chemists have had to develop were unit measurements for characteristics like volume, mass, pressure, and temperature.

Having common units of measurement makes comparing experimental results and detecting patterns of behavior in chemical reactions much easier.

The Gas Laws

We have mentioned briefly several gas laws which were important in the quest for the nature of elements. To review

Families of matter

Take a look at Mendeleev's early draft of the periodic table. In this version, we see eight columns. Elements in the first column on the left "Gruppe 1" or Group 1, combine in the ratio 2:1 with oxygen. You can see sodium (Na) and potassium (K) listed in column. Their placement here means they combine in this 2:1 ratio with oxygen, so the formula for sodium oxide would be Na2O and for potassium oxide would be K2O.

The next column, Gruppe II, combines in a 1:1 ratio with oxygen. For example, magnesium oxide is MnO.

The next column, Gruppe III, contains elements that combine in a 2:3 ratio with oxygen. So aluminum oxide is Al2O3.

  • How does carbon in group IV combine with hydrogen? with oxygen?
  • What does the number 23 in "Na = 23" mean?
  • How are the elements arranged within each column?

Mendeleev's periodic table has been expanded and filled in; there are now 92 elements found in nature as well as a number of "trans-uranium" elements which can be produced in the lab and which have very short lifetimes before they decay into one of the more stable elements.

Look at the layout of a modern periodic table, and read about the different groups of elements.

  • What are the characteristics of metals in general?
  • What are the characteristics of the alkaline and earth alkaline metals?
  • What are the characteristics of the transition metals?
  • What are the characteristics of non-metals?
  • What distinguishes halogens from other elements?
  • What distinguishes noble gases from other elements?

Study/Discussion Questions

Further Study On your Own (Optional)