group 2 elements

Metallic Character:
Increases down the group due to increased electropositive character.

Density:
Generally increases from top to bottom as atomic mass increases.

Melting and Boiling Point:
Higher than alkali metals due to smaller size and stronger metallic bonds. No regular trend down the group.

Flame Coloration:

  • Be, Mg: No characteristic color (small size, high ionization energy)
  • Ca: Brick red
  • Sr: Crimson red
  • Ba: Sea green

Important Calcium Compounds

CompoundCommon Name
CaOQuick lime
Ca(OH)₂Slaked lime
CaCO₃Limestone

Chemical Reactions and Applications
Q: When water is added to compound A of calcium, a solution of compound B is formed. When CO₂ is passed into this solution, it turns milky due to the formation of compound C. Identify the compounds A, B, and C. Write the chemical reactions involved. Give the biological role of Ca²⁺.

A:

  • Compound A: CaO (Quick lime)
  • Compound B: Ca(OH)₂ (Slaked lime)
  • Compound C: CaCO₃ (Calcium carbonate)

Reactions:

  • CaO + H₂O → Ca(OH)₂
  • Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

Biological Role of Ca²⁺:

  • Essential for bone and teeth formation
  • Involved in blood clotting
  • Important for muscle contraction and nerve function

Important Questions with Answers

  1. What are the trends in metallic character, density, and melting/boiling points in group 2 elements?
    Answer:
    Metallic character increases down the group.
    Density generally increases from top to bottom.
    Melting and boiling points are higher than alkali metals but do not show a regular trend.

  2. Explain the flame coloration of group 2 elements with examples.
    Answer:
    Be and Mg do not impart color to the flame.
    Ca gives a brick red color, Sr gives crimson red, and Ba gives sea green color.

  3. Write the chemical reactions when quick lime reacts with water and then with CO₂.
    Answer:
    CaO + H₂O → Ca(OH)₂
    Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

  4. State the biological importance of Ca²⁺ ions.
    Answer:
    Ca²⁺ ions are essential for bone and teeth formation, blood clotting, muscle contraction, and nerve function.

  5. Match the following:

  • CaO: Quick lime
  • Ca(OH)₂: Slaked lime
  • CaCO₃: Limestone