Lecture Notes: Dmitri Mendeleev and the Periodic Table

Introduction

• Dmitri Mendeleev: Russian chemist and inventor.
• Contribution: Devised the periodic table in the mid-19th century.
• Significance: Organized known elements and predicted new ones.

Structure of the Periodic Table

• Arrangement: Elements arranged in order of increasing atomic number (number of protons).
• Element Box Components:
  • Elemental Symbol: One or two-letter symbol (e.g., Na for Sodium).
  • Atomic Number: Number of protons.
  • Mass Number: Total number of protons and neutrons.

Periods and Groups

• Repeating Patterns: Chemical properties repeat at regular intervals.
• Rows (Periods): New row each time the pattern repeats.
• Columns (Groups):
  • Elements in a vertical column share similar chemical properties.
  • Group numbering starts from 1 on the far left to 7.

Special Groups and Trends

• Group 0 (Noble Gases): Far-right group, not numbered as 8.
  • Full outer electron shells; very unreactive.
• Alkali Metals (Group 1):
  • One electron in the outer shell.
  • Similar properties, e.g., react violently with water.
  • Reactivity increases down the group.
• Halogens (Group 7):
  • Seven electrons in the outer shell.
  • Reactivity decreases down the group.

Electron Configuration

• Electrons in Outer Shells: Determines an element's reactivity.
• Group Number: Indicates the number of electrons in the outer shell.

Metals and Nonmetals

• Separation: Zigzag line from aluminum to polonium.
  • Metals: To the left (more abundant than nonmetals).
  • Nonmetals: To the right.
• Transition Metals: Special block of elements between groups 2 and 3.

Miscellaneous

• Variations in Periodic Tables:
  • Different layouts exist (e.g., positions of mass and atomic numbers).
  • All tables provide the same information, only presented differently.
  • Atomic number is always the smaller number.

Conclusion

• Utility: Periodic table is a fundamental tool in chemistry.
• Further Study: Future videos will cover specific groups and properties of metals vs. nonmetals.

Note: Always check for the periodic table provided in exams as it will be similar to the ones discussed in this lecture.