Modern Periodic Table

Introduction

• Review of previous classification efforts: Dobereiner's Triads, Newlands' Law of Octaves, and Mendeleev's Periodic Table.
• Focus on the Modern Periodic Table.
• We'll build the periodic table from a blank table, focusing on the first 20 elements (up to Calcium).

Structuring the Table

• Rows and Columns: The periodic table has rows called periods and columns called groups.
• Numbering: Rows are numbered 1 to 7, columns are numbered 1 to 18.

Atomic Number

• Definition: Atomic number = number of protons in an element's nucleus.
• Significance: Modern periodic table is based on atomic number, which determines chemical properties more accurately than atomic mass.
• Moseley's Contribution: Proved the fundamental property of atomic number.

Filling the Table

• First Element: Hydrogen with atomic number 1.
• Next Elements: Helium (2), Lithium (3), Beryllium (4), Boron (5), Carbon (6), Nitrogen (7), Oxygen (8), Fluorine (9), Neon (10), Sodium (11), Magnesium (12), Aluminium (13), Silicon (14), Phosphorus (15), Sulfur (16), Chlorine (17), Argon (18), Potassium (19), Calcium (20).
• Each additional element: One extra proton and one extra electron.

Period Significance

• Number of Electron Shells: Period number = number of electron shells.
• Examples:
  • Hydrogen (1 shell)
  • Oxygen (2 shells)
  • Aluminium (3 shells)
  • Calcium (4 shells)

Electronic Configuration

• Examples:
  • Hydrogen: 1 proton, 1 electron, 1 shell
  • Oxygen: 8 protons, 8 electrons; configuration: 2, 6
  • Aluminium: 13 protons, 13 electrons; configuration: 2, 8, 3
  • Calcium: 20 protons, 20 electrons; configuration: 2, 8, 8, 2

Group Significance

• Grouping by Properties: Similar elements are grouped together (like items in a grocery store).
• Group Examples:
  • Group 1: Alkali metals (similar valency and properties)
  • Group 2: Alkaline earth metals (similar valency and properties)
  • Group 17: Nonmetals with same valency
• Reason for Similar Properties: Same number of valence electrons.

Detailed Group Analysis

• Group 1 Elements (e.g., Hydrogen, Lithium, Sodium, Potassium)
  • Common trait: 1 valence electron.
• Group 2 Elements (e.g., Beryllium, Magnesium, Calcium)
  • Common trait: 2 valence electrons.

Old and New Group Numbering Schemes

• New Scheme: Numbers from 1 to 18.
• Old Scheme: Roman numerals and alphabets A and B.
  • Group 1: 1A
  • Group 2: 2A
  • Group 13-18: 3A, 4A, 5A, 6A, 7A, 0
  • Groups 3-12: B groups (3B to 2B)

Element Categories and Coloring

• Four Broad Categories: Metals, Non-metals, Metalloids, Noble gases.
• Special Group Names:
  • Group 1: Alkali metals
  • Group 2: Alkaline earth metals
  • Group 13: Boron family
  • Group 14: Carbon family
  • Group 15: Nitrogen family
  • Group 16: Oxygen family (Chalcogens)
  • Group 17: Halogens
  • Group 18: Noble gases

Full Periodic Table

• 7 Periods, 18 Groups.
• Lanthanides and Actinides:
  • Lanthanides: Elements 57-71
  • Actinides: Elements 89-103

Merits of the Modern Periodic Table

• Correction of Anomalies: Fixed issues in Mendeleev's table.
• Isotopes: Same position due to identical atomic numbers.
• Better arrangement: Based on atomic numbers, improving the arrangement (e.g., Cobalt and Nickel).
• Special Position of Hydrogen: Shows properties similar to both Group 1 (Alkali metals) and Group 17 (Halogens).

Conclusion

• Mastering the Table: Practice creating and understanding the periodic table.
• Future Topics: Trends in the periodic table will be covered in another video.
• Further Learning: Follow up on quizzes and questions.

---

Feel free to subscribe to the channel and check out additional resources for more detailed studies.