Chapter 2 Periodic System

Question 1

1. What are the differences in the meaning of the following terms: ‘periodic law’, ‘periodic system’ and ‘periodic table’?

Answer 1

Question 2

2. Elaborate the following statement: “The periodic law has been described as the most characteristic and fundamental law of chemistry, but remains nevertheless approximate and vague.”

Answer 2

Question 3

3. What are the main conclusions of Mendeleev’s first article on the periodic law?

Answer 3

Question 4

4. On which 2 properties did Mendeleev based his ordering of the chemical elements? Give a definition of these properties.

Answer 4

Question 5

5. Why must the periodic tables that decorate the walls in science museums or university buildings, and typically display a variety of samples of the elements be considered as incorrect representations of the periodic law?

Answer 5

Question 6

6. Which problems led to a questioning of the validity of the periodic law and have threatened the periodic table? How have these problems been solved?

Answer 6

Question 7

7. Why is it not fair to give all credit for the discovery of the periodic law to Mendeleev? Why became Mendeleev’s name linked to the periodic table in the course of history?

Answer 7

Question 8

8. What are the main later developments of the periodic system after Mendeleev’s contributions in 1869–1870?

Answer 8

Question 9

9. What is the difference between equivalent weight and atomic weight?

Answer 9

Question 10

10. Why is ordering of the elements according to increasing atomic number more fundamental than ordering according to increasing atomic weight?

Answer 10

Question 11

11. Why were, prior to 1949, thorium, protactinium, and uranium considered as transition metals? What caused their relocation to the actinide series?

Answer 11

Question 12

12. What are differences between chemical (periodic) tables and electron configuration (periodic) tables? What are advantages and disadvantages of both types of periodic tables?

Answer 12

Question 13

13. Why is it impossible to define “the best periodic table” or “the ideal periodic table”?

Answer 13

Question 14

14. What are advantages and disadvantages of the short form of the periodic table?

Answer 14

Question 15

15. Why did the medium-long form of he periodic table become over the years more popular than the short form?

Answer 15

Question 16

16. Why has the IUPAC recommendation of numbering the groups in the periodic table by the Arabic numerals 1 to 18 been criticized by chemists?

Answer 16

Question 17

17. What are the features of the left-step periodic table (LSPT)? Why did this form of the periodic table not become popular?

Answer 17

Question 18

18. What is the step-pyramid periodic table? What are its pros and cons?

Answer 18

Question 19

19. What is an extended periodic table? What is the maximum number of chemical elements?

Answer 19

Question 20

20. What is the original meaning of the terms ‘transitional elements’ or ‘transition elements’? What do we understand at present under the term ‘transition element’?
21. Why do some chemists not consider ‘transition elements’ and ‘d-block metals’ as synonyms?

Answer 20

Question 21

22. What is the primary and secondary classification of elements?

Answer 21

Question 22

23. What are the different options to place hydrogen in the periodic table? What are the pros and cons of these different options?

Answer 22

Question 23

24. Are the Group 3 elements scandium–yttrium–lanthanum–actinium or scandium–yttrium–lutetium–lawrencium? Give arguments in favor or against these two options.

Answer 23

Question 24

25. What are the advantages and disadvantages of the medium-long form of the periodic table?

Answer 24

Question 25

26. Are zinc, cadmium and mercury d-block or p-block elements?

Answer 25

Question 26

27. What are primary, secondary and tertiary analogies between elements?

Answer 26

Question 27

28. What are isodonor, isoacceptor and isovalent elements?

Answer 27