Classification of Elements and Periodicity in Properties

Importance of the Periodic Table

• Fundamental in chemistry
• Organizes chemical elements into a coherent structure
• Essential for understanding trends and properties of elements

Learning Objectives

• Understand the development and organization of the Periodic Table
• Learn about Periodic Law and significance of atomic numbers
• Classify elements based on blocks (s, p, d, f)
• Recognize periodic trends in chemical and physical properties

Need for Classification

• Historical discovery of elements
• The challenge of studying numerous elements and compounds
• Systematic classification simplifies study and predicts new properties

Genesis of Periodic Classification

• Early attempts like Dobereiner's triads and Newlands' Law of Octaves
• Mendeleev's Periodic Table based on atomic weights
• Mendeleev's prediction of undiscovered elements
• Modern Periodic Law: Properties are periodic functions of atomic numbers

Modern Periodic Law and Table

• Moseley's contribution with X-ray spectra
• Modern Periodic Law: Properties depend on atomic numbers
• Periodic Table arranged in periods (horizontal rows) and groups (vertical columns)

Nomenclature of Elements

• IUPAC's role in naming elements with atomic numbers > 100
• Elements are given temporary names based on their atomic number

Electronic Configurations and Periodic Table

• Connection between electronic configuration and element position
• Understanding period-based and group-based electronic configurations

Types of Elements Based on Blocks

• s-Block Elements: Group 1 and 2, highly reactive metals
• p-Block Elements: Groups 13-18, includes nonmetals and noble gases
• d-Block Elements: Transition metals, exhibit variable valences
• f-Block Elements: Lanthanoids and actinoids, inner-transition metals

Metals, Non-Metals, and Metalloids

• Metals: Majority of elements, conductive, malleable
• Non-Metals: Found on the right side of the table, poor conductors
• Metalloids: Exhibit properties of both metals and non-metals

Periodic Trends

• Atomic Radius: Decreases across periods, increases down groups
• Ionic Radius: Similar trend to atomic radius
• Ionization Enthalpy: Increases across a period, decreases down a group
• Electron Gain Enthalpy: Becomes more negative across a period
• Electronegativity: Increases across periods, decreases down groups

Chemical Reactivity

• Trends in reactivity related to electronic configuration
• Metals are more reactive on the left, non-metals on the right
• Oxides vary from basic on the left to acidic on the right

Summary

• Periodic Law and Table development
• Classification based on electronic configurations
• Trends in atomic size, ionization energy, electronegativity, etc.

Exercises

• Questions exploring understanding of periodic trends, element properties, and Table organization