THE-PERIODIC-TABLE-NOTES-2022-1

The Periodic Table

  • Definition: The Periodic Table is organized by increasing atomic number.

  • Classification of Elements:

    • Metals

    • Semi-metals

    • Non-metals

  • Groups:

    • Elements with the same number of valence electrons are aligned vertically in columns (groups).

    • Valence Electrons: Electrons in the outer shell that determine chemical properties.

  • Periods:

    • Horizontal rows representing the number of electron shells.

Groups and Electron Configurations

  • Overview:

    • Each group has a characteristic number of valence electrons:

      • Group 1 (Alkali Metals): 1 valence electron

      • Group 2 (Alkaline Earth Metals): 2 valence electrons

      • Group 7 (Halogens): 7 valence electrons

      • Group 8 (Noble Gases): 8 valence electrons (full outer shell)

  • Electron Configurations:

    • Group 1:

      • Li: 2, 1

      • Na: 2, 8, 1

      • K: 2, 8, 8, 1

    • Group 2:

      • Be: 2, 2

      • Mg: 2, 8, 2

      • Ca: 2, 8, 8, 2

    • Group 7:

      • F: 2, 7

      • Cl: 2, 8, 7

    • Group 8:

      • He: 2, 0

      • Ne: 2, 8, 0

      • Ar: 2, 8, 8, 0

Special Named Groups

  • Group Names:

    • Group 1: Alkali Metals

    • Group 2: Alkaline Earth Metals

    • Group 6: Chalcogens

    • Group 7: Halogens

    • Group 8: Inert Gases/Noble Gases

Periods and Representative Elements

  • Periods: Horizontal rows (I to VIII) signify the energy levels.

  • Representative Elements: Elements in groups that show predictable patterns in behavior.

Transition Elements

  • Location: Situated between Groups II and III, featuring complex electron configurations.

Physical and Chemical Properties of Group 1 (Alkali Metals)

  • Common Elements: Lithium, Sodium, Potassium.

  • Physical Properties:

    1. Metals

    2. Less dense than water (float)

    3. Silvery and shiny when freshly cut

    4. Low melting and boiling points.

  • Chemical Properties:

    • Groups exhibit similar reactions due to identical valence electron counts.

Group 1 Chemical Reactivity

  • Reactions with Water:

    1. Lithium: Moves on surface, produces hydrogen gas.

    2. Sodium: Melts, moves, produces hydrogen gas (stronger reaction).

    3. Potassium: Most reactive, produces hydrogen gas, burns with a blue flame.

    • All reactions are exothermic.

    • Reactivity Order: Lithium < Sodium < Potassium.

  • Reactions with Chlorine:

    • All metals burn with characteristic colored flames:

      • Lithium: Bright white

      • Sodium: Yellow

      • Potassium: Violet.

    • All reactions are exothermic.

    • Reactivity Order: Lithium < Sodium < Potassium.

  • Reactions with Oxygen:

    • All metals produce white oxide salts; characteristic flames:

      • Lithium: Red

      • Sodium: Yellow

      • Potassium: Violet.

    • All reactions are exothermic.

    • Reactivity Order: Lithium < Sodium < Potassium.

Group 7 (Halogens)

  • Common Examples: Chlorine, Bromine, Iodine.

  • Physical Properties:

    1. Non-metals

    2. Chlorine: Green gas, Bromine: Reddish-brown liquid, Iodine: Black solid.

    3. All are poisonous.

  • Reactions:

    • React with iron wool producing a brown gas and a solid.

    • Reactivity Order: Iodine < Bromine < Chlorine.

Group 8 (Noble Gases)

  • Common Examples: Helium, Neon, Argon.

  • Physical Properties:

    1. Non-metals

    2. Gases

    3. Colorless.

  • Chemical Properties:

    • Noble gases are unreactive due to a full outer shell of eight electrons.

Exercise: Place Elements in Table

  • Element Placements (use imaginary symbols):

    • A: Atomic number 6 (Carbon)

    • B: Inert gas in Period 3 (Argon)

    • C: Atomic number 7 (Nitrogen)

    • D: Black solid in Group 7 (Iodine)

    • E: Period 3, seven valence electrons (Chlorine)

    • F: Most reactive alkali (Potassium)

    • G: Most reactive chalcogen (Oxygen)

    • H: Element with four electrons in M shell (Silicon)

    • I: Atomic structure diagram with p = 16, n = 32.