ICSE Class 9 Chemistry Chapter 04 The Language of Chemistry

4 - The Language Of Chemistry

Scope Of Syllabus

Symbol of an element; valency; formulae of radicals and formulae of compounds. Balancing of simple chemical equations.

Symbol - definition; symbols of the elements used often.

Valency - definition; hydrogen combination and number of valence electrons of the metals and non-metals; mono, di, tri and tetravalent elements.

Radicals - definition of radicals; formula and valencies of the radicals and formula of compounds.

Chemical equation - definition and examples of chemical equations with one reactant and two or three products, two reactants and one product, two reactants and two products and two reactants and three or four products; balancing of equations. (By partial equation method and hit and trial method).

Important Points To Remember

1. The simplified, abbreviated names of the elements are called symbols. The names of the elements represented are in English, Latin or Greek.

2. A symbol is generally represented by the first alphabet of an atom of the element in capital letter.

3. In case, the name of more than one element begins with the same alphabet, then the first two alphabets are chosen. In this case, the first alphabet is written in capital and the second alphabet is written in small letter.

4. Symbols of some common elements are given in the following table:

Teacher's Note

Element symbols are like abbreviations we use in texting - instead of writing the full word, we use a short code. Just as "Cu" represents Copper, "Na" represents Sodium, these symbols save time and space in chemistry just as abbreviations do in everyday communication.

5. Qualitatively symbol represents a specific element and one atom of an element.

For example, O represents one element of oxygen.

O represents one atom of oxygen.

6. Radicals are the group of atoms of different elements which behave as a single unit, having their own combining capacity and existing independently.

7. Positive radicals are called basic radicals or cations.

8. Negative radicals are called acidic radicals or anions.

9. Valency is the combining capacity of an element.

10. Valency represents the number of hydrogen atoms which combine directly or indirectly with one atom of an element.

11. Valency is equal to the number of electrons lost, gained or shared by an element during chemical bond formation.

12. The valency of hydrogen and metals is positive whereas non-metals have negative valency.

13. Certain elements exhibit more than one valency by losing electrons present in the penultimate shell, such valency is called as variable valency.

14. If the element has two different positive valencies, then suffix-'ic' is attached at the end of the name of the metal for the higher valency and suffix-'ous' is attached at the end of the name of the metal for the lower valency.

For example, Lead (Plumbum) exhibits two valencies + 2 and + 4. The lower valency of lead (Pb2+) is named as plumbous. The higher valency of lead (Pb4+) is named as plumbic.

Teacher's Note

Understanding valency is like understanding friendship - some elements "want" to gain friends (electrons), some want to lose friends, and some are flexible about it depending on the situation. Just as we call people by different names based on their roles, we use different names for elements based on their valency.

Positive Radicals

Negative Radicals

Teacher's Note

Radicals work like team members in chemistry - some carry a positive charge (wanting to give away electrons) and some carry a negative charge (wanting to gain electrons). When they combine, they balance each other out, just like a balanced team has both leaders and supporters working together.

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