2.6 Elements and compounds

Natural sciences

Grade 8

Matter: classification

Module 19

Elements and compounds

Elements

• One of the basic sets of information in the natural sciences is represented in the list of elements.
• We refer to it as the Periodic Table.
• There are 112 elements in this table, and 90 of them occur naturally on our planet and as far as we know in the surrounding space.
• The rest are manufactured synthetically in laboratories.
• The elements are arranged according to qualities like mass and density, and according to how they are chemically compounded.

Assignment

• Collect information on Mendeleev (1834-1907) ) and on how he devised the periodic table.
• Add this to your poster about scientists through the ages.

http://smallfry.dmu.ac.uk/chem/tables

Class activity: listening skills

Listen attentively to the educator’s explanation and complete the following.

The Periodic Table

1. The horizontal lines are known as

2. The vertical lines are known as

3. In what part of the periodic table do we find the metals?

4. Which metals are stored under paraffin? Why?

5. What do we call these metals?

6. In what part of the periodic table do we find the non-metals?

7. Which non-metal is stored under water? Why?

8. Where do we find most of the gases? Explain this

9. Which gases do not react with other substances?

10. What is the name of this group of gases?

11. Name the lightest gas

12. Which elements occur in liquid phase at room temperature?

13. Which element sublimates?

14. In which phase do most elements occur at room temperature?

15. Why do we place particular elements in the same group?

Elements and their Symbols

• Transfer the names of the elements and their symbols to the periodic table on the following page.
• Apply colour to indicate the different groups.]LO 2.2]

Assessment of listening skills

Test yourself: are you able to answer questions 1 – 15 without referring to the answers?

[LO 2.1]

Group work: quiz

Any question that cannot be answered must be investigated.

Which element do we have here ?

[LO 2.1]

 Do you know the following? 

Some elements, like

CARBON

occur in various forms:

diamonds

coal, and the

graphite in your pencil!

http://education.jlab.org/itselemental/ele006

http://mineral.galleries.com

Assessment

Learning outcome 2: Constructing science knowledge

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

We know this when the learner

2.1 is able to recall significant information;

2.2 is able to categorise information.

Memorandum

1. periods

2. groups

3. below left and in the transition block

4. Li, Na, K – reactive with water vapour

5. Alkali metals

6. Below right

7. P – reactive with oxygen

8. On the extreme right

9. Gases on extreme right

10. Noble gases

11. H

12. Br and Hg

13. Iodine

14. Solid substance

15. Corresponding qualities

The PERIODIC TABLE OF ELEMENTS

1. periods

2. groups

3. below left and in the transition block

4. Li, Na, K – reactive with water vapour

5. Alkali metals

6. Below right

7. P – reactive with oxygen

8. On the extreme right

9. Gases on extreme right

10. Noble gases

11. H

12. Br and Hg

13. Iodine

14. Solid substance

15. Corresponding qualities

ELEMENTS AS SYMBOLS

GROUP WORK:QUIZ

1. Mg

2. Titanium

3. Fe

4. He

5. Cu

6. H

7. Ag

8. S

9. Br

10. Ar

11. Co

12. Ca

13. P

14. Si

16. Cl

17. K

18. Cr

19. Ne

20. Cyanide

21. Al

22. N

23. Kr

24. Na

25. Zinc

CLASS ACTIVITY: RECOGNITION OF METALS AND NON-METALS

Metals:

Non-metals:

1. shiny, hard

2. gold

3. demand

4. study of metals

5. alloy

6.

7. Pliable – long threads stretched out.

Malleable – hammered into thin plates/sheets.

GROUP WORK: QUIZ

1. Mg

2. Titanium

3. Fe

4. He

5. Cu

6. H

7. Ag

8. S

9. Br

10. Ar

11. Co

12. Ca

13. P

14. Si

16. Cl

17. K

18. Cr

19. Ne

20. Cyanide

21. Al

22. N

23. Kr

24. Na

25. Zinc