Dmitri Mendeleev and the Periodic Table

Introduction to Mendeleev

• Russian chemist and inventor.
• Devised the periodic table in the mid-19th century.
• Predicted existence of elements not yet discovered.

Structure of the Periodic Table

• Organized by increasing atomic number (number of protons).
• Elements read left to right, top to bottom.
• Element Box Components:
  • Top Left: Mass number (total protons and neutrons).
  • Bottom Left: Atomic number (protons).
  • Right: Elemental symbol (e.g., Na for sodium).

Patterns in the Periodic Table

• Elements show repeating chemical properties, forming rows called periods.
• Vertical columns called groups, numbered 1 to 7; far right as group 0, not 8.
• Elements in the same group have similar chemical properties due to the same number of outer shell electrons.

Understanding Groups

• Group 2: Elements with 2 electrons in the outer shell.
• Group 1 (Alkali Metals): 1 outer shell electron (e.g., lithium, sodium), react violently with water.
• Group 7 (Halogens): 7 outer shell electrons, become less reactive down the group.
• Group 0 (Noble Gases): Full outer shells, very unreactive.

Metals and Non-metals

• Zigzag line separates metals (left) from non-metals (right).
• More metals than non-metals.
• Transition metals located in the middle.

Variations in Periodic Tables

• Different presentations exist with variations in mass and atomic number positions.
• Mass number is larger; atomic number is smaller.
• Exam periodic tables similar to the version discussed.

Conclusion

• Further exploration on group 1, 7, 0 elements, and metal vs. non-metal differences in future content.