Lecture: The Periodic Table of the Elements

Basics of the Periodic Table

• Columns are called groups.
• Rows are called periods.

Group Characteristics

• Group 1: Alkali Metals

  • Includes lithium, sodium, potassium, rubidium, cesium, and francium.
  • Very reactive, especially with water.
  • Reactivity increases down the group.
  • Low melting points.
  • Low density; lithium and sodium float on water.

• Group 2: Alkaline Earth Metals

  • Includes beryllium, magnesium, calcium, strontium, barium, and radium.
  • Reactive, but less so than alkali metals.

• Transition Metals

  • Multiple oxidation states; e.g., Iron (Fe) can be +2 or +3, Copper (Cu) can be +1 or +2.

• Group 16: Calcogens

  • Includes oxygen, sulfur, selenium, tellurium, and polonium.

• Group 17: Halogens

  • Includes fluorine, chlorine, bromine, and iodine.
  • Non-metals with similar reactivity.

• Group 18: Noble Gases

  • Includes helium, neon, argon, krypton, xenon, and radon.
  • Chemically inert (non-reactive).

Electron Configuration & Ion Formation

• Valence electrons correspond to group numbers (1A, 2A, etc.).

  • Group 1 has 1 valence electron, Group 2 has 2, etc.
  • Group 18 (noble gases) have full outer shells, making them stable.

• Metals

  • Electrical conductors, malleable, ductile.
  • Lose electrons to form positive ions (cations).

• Non-metals

  • Poor conductors, brittle.
  • Gain electrons to form negative ions (anions).

• Metalloids

  • Intermediate properties; semiconductors (e.g., silicon, germanium).

Important Terms

• Lanthanides and Actinides

  • Lanthanides follow element 57.
  • Actinides follow element 88.

• Element Symbols and Atomic Numbers

  • Element symbol represents the element; e.g., H for Hydrogen.
  • Atomic number equals the number of protons.
  • Atomic weight is the average mass of an element's isotopes.

Isotopes and Atomic Mass

• Isotopes differ in neutron number but share the same proton number.
• Example: Carbon has isotopes C-12, C-13, and C-14.

Common Elements and Their Uses

• Hydrogen (H): Found in stars.
• Helium (He): Used in balloons.
• Lithium (Li): Found in batteries.
• Sodium (Na): Component of table salt.
• Iron (Fe): Common metal.
• Copper (Cu): Used in wiring.

Diatomic and Allotropic Forms

• Diatomic molecules: nitrogen (N2), oxygen (O2), fluorine (F2), etc.
• Allotropes: Graphite and diamond are both forms of carbon.

Rare and Radioactive Elements

• Uranium: Used in nuclear fission.
• Radon: Radioactive, can accumulate in homes.

Additional Notes

• Understanding the periodic table involves knowing the naming and properties of elements and their groups.
• It's important to recognize common element symbols and their applications in everyday life.

This lecture covered the fundamental concepts of the periodic table, including the characteristics of various groups, the formation of ions, and the unique properties of metals, non-metals, and metalloids.