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  Chemistry Course – The Periodic Table and Elements

 


What Is the Periodic Table?

The Periodic Table of Elements is a systematic arrangement of all known chemical elements.

  • Created by Dmitri Mendeleev in 1869.
  • Organized by increasing atomic number (Z).
  • Groups elements with similar chemical properties into columns.

👉 It is the “map of chemistry,” showing trends in reactivity, size, and bonding.

2️⃣ Structure of the Periodic Table

  • Periods (rows): Show the number of electron shells.
  • Groups (columns): Contain elements with similar valence electron configurations and chemical properties.

Main categories of elements:

  • Metals (left side, conductors, malleable, shiny).
  • Nonmetals (right side, poor conductors, many gases).
  • Metalloids (stair-step line, with mixed properties).

3️⃣ Element Families (Groups)

  • Group 1: Alkali Metals (Li, Na, K, …)
    • Very reactive, soft, react violently with water.
  • Group 2: Alkaline Earth Metals (Mg, Ca, …)
    • Reactive, form strong ionic bonds.
  • Group 17: Halogens (F, Cl, Br, I, …)
    • Very reactive nonmetals, form salts with metals.
  • Group 18: Noble Gases (He, Ne, Ar, …)
    • Stable, inert, full outer shells.

4️⃣ Periodic Trends

The periodic table reveals predictable trends:

  • Atomic Radius → decreases across a period, increases down a group.
  • Electronegativity → increases across a period, decreases down a group.
  • Ionization Energy → increases across a period, decreases down a group.
  • Metallic Character → decreases across a period, increases down a group.

5️⃣ Importance in Chemistry

The periodic table allows chemists to:

  • Predict element reactivity.
  • Understand bonding behavior.
  • Identify element families and their applications.
  • Guide the discovery of new elements.

6️⃣ Applications in Real Life

  • Sodium (Na): essential in biological processes, table salt.
  • Calcium (Ca): bones, teeth, and building materials.
  • Chlorine (Cl): disinfection, PVC plastics.
  • Neon (Ne): neon lights.
  • Uranium (U): nuclear energy.

7️⃣ Simple Exercises

  1. Which family does chlorine (Cl) belong to?
  2. Why are noble gases chemically inert?
  3. Compare the electronegativity of oxygen (O) and sodium (Na).