Page 34 - Chemistry_Form_2

Chemistry
for Secondary Schools

Exercise 2.1

1. Why were the noble gases not included in Mendeleev’s periodic table?

2. How does the electronic configuration of nitrogen compare to that of
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phosphorus?

3. Explain the significance of the Law of Octaves in understanding periodic
trends.

4. Mendeleev left gaps in his periodic table. Predict how these gaps demonstrate

his understanding of properties of elements.

5. Mendeleev used atomic masses to arrange elements. If you were to use atomic
numbers, how would this impact the organisation of the periodic table?

6. How did the Mendeleev’s and Newlands’ works contribute to understanding
the relationships between elements’ physical and chemical properties.

Electronic configuration and element positioning in the periodic table

Task 2.2

Use reliable online resources to analyse the relationships between electronic
configurations and the positions of elements in the periodic table.

The arrangement of electrons in an atom follows a specific pattern known as
electronic configuration. This configuration determines the positioning of

elements in the periodic table and their properties. Elements with similar valence
electron configurations share common properties and belong to the same group
in the periodic table. Elements are arranged in groups based on the number of
electrons in their outermost shells. Elements in the same group exhibit similar
chemical properties because they have the same number of valence electrons.
Valence electrons are the outermost electrons of an atom that are involved in
forming chemical bonds. The groups are labelled using Roman numerals (I to

VIII), with the group number corresponding to the number of electrons in the
outermost shell as shown in Figure 2.1.

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