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Chapter 17 — Chapter 17 — Group 2 Elements
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📘Easy summary
Group 2 elements (Be, Mg, Ca, Sr, Ba) are s-block elements, also called alkaline earth metals due to their metallic nature and occurrence in the earth crust. Their reactivity lies between the highly reactive alkali metals and the less reactive transition metals. All have two electrons in their outermost s subshell (ns²), so they show similar chemical properties, but properties vary down the group. Metallic radius (112 → 215 pm for Be → Sr) and ionic radius increase; first and second ionization energies and electronegativity decrease; standard electrode potentials become more negative (−1.97 V for Be to −2.91 V for Ba). After losing two electrons they become stable M²⁺ ions. Reactivity increases from Be to Ba due to increase in size and shielding effect and decrease in ionization energy, which makes removal of electrons easier. Reactivity series: Be ＜ Mg ＜ Ca ＜ Sr ＜ Ba. Trends in melting point and density are related to the different packing of metal atoms.
⭐Key points
- Valence shell ns²; form M²⁺ ions.
- Size increases, ionization energy decreases down the group.
- Reactivity: Be < Mg < Ca < Sr < Ba.
- Mg is part of chlorophyll; Mg, Ca, Sr, Ba give firework colours.
🔬Diagram
🌿Real-life example
Barium reacts with water much more vigorously than beryllium, which does not react with water at all.
💡Exam tip
- Always explain reactivity with three words: size, shielding, ionization energy.
✅Quick check
1. The most reactive Group 2 element is:
2. The valence shell configuration of Group 2 is:
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