Bihar Board - Class 11 - Chemistry - Chapter 3: Classification of Elements and Periodicity in Properties Handwritten Notes

The "Classification of Elements and Periodicity in Properties" chapter introduces the organization of elements in the periodic table. It explains how elements are classified based on their atomic structure and how their properties follow a periodic trend. This chapter is essential for understanding how elements relate to one another and why certain patterns appear in their properties across periods and groups.

Key Points:

1. Mendeleev's Periodic Table:

   • Dmitri Mendeleev arranged elements based on increasing atomic mass, leading to the creation of the periodic table.
   • Elements with similar properties were placed in the same group.

2. Modern Periodic Table:

   • The modern periodic table is organized by increasing atomic number, not atomic mass, as per Moseley's discovery.
   • It is divided into periods (horizontal rows) and groups (vertical columns).

3. Periodic Law:

   • The periodic law states that the properties of elements are a periodic function of their atomic numbers, meaning elements with similar properties recur at regular intervals.

4. Groups and Periods:

   • Groups: Vertical columns in the periodic table, consisting of elements with similar chemical properties.
   • Periods: Horizontal rows in the periodic table, indicating the number of electron shells.

5. Classification of Elements:

   • Elements are classified into metals, non-metals, and metalloids based on their physical and chemical properties.
   • Metals are typically good conductors of heat and electricity, while non-metals are poor conductors. Metalloids have properties of both metals and non-metals.

6. Trends in the Periodic Table:

   • Atomic size decreases across a period and increases down a group.
   • Ionization energy increases across a period and decreases down a group.
   • Electronegativity increases across a period and decreases down a group.
   • Electron affinity generally becomes more negative across a period and less negative down a group.

7. Transition Elements:

   • The transition elements (d-block elements) exhibit a wide range of properties and are known for their ability to form multiple oxidation states.

8. Noble Gases:

   • Noble gases are chemically inert due to their full outer electron shells. They do not readily react with other elements.

Conclusion:

The chapter on "Classification of Elements and Periodicity in Properties" provides an understanding of how elements are systematically organized in the periodic table and how their properties follow periodic trends. This classification helps predict the behavior and reactivity of elements, forming the foundation for more advanced studies in chemistry. By grasping the periodic law and the arrangement of elements, students can better understand chemical behavior and trends that influence reactions and element interactions.

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