Alkali Earth Metals

Why do alkaline earth metals easily form 2⁺ cations?

Because they have two valence electrons, low Z-effective, and low ionization energies.

What trend is observed in ionization energy and melting point down Group 2?

Both decrease as atomic size increases.

Which Group 2 elements can form covalent bonds and why?

Beryllium and magnesium, due to their small size and high charge density, which allows them to polarize other atoms.

What types of bonds do the heavier Group 2 metals usually form?

Mostly ionic bonds, especially in halide salts and hydrates.

How is beryllium prepared?

By reacting beryllium chloride with magnesium or calcium:
BeCl₂ + (Mg or Ca) → Be + (Mg or Ca)Cl₂

How is magnesium prepared industrially?

• Electrolysis of molten salt mixtures (MgCl₂ + CaCl₂ + NaCl):
  (MgCl₂ + CaCl₂ + NaCl)(l) + 2e⁻ → Mg + …

• Or by thermal reduction:
  MgO + C → Mg + CO

How are heavier Group 2 metals (Ca, Sr, Ba) prepared?

By metal displacement using sodium:
MCl₂ + 2Na → M + 2NaCl
(M = Ca, Sr, Ba)

What kinds of compounds does beryllium form?

• Covalent compounds (e.g., BeO, BeS, BeF₂)

• Forms organometallic compounds by bonding with carbon

What types of compounds does magnesium form?

• Grignard reagents (RMgX, covalent)

• Ionic compounds like MgCl₂, MgO

How do heavier alkaline earth metals behave with halide ions in water?

They form lattice hydrates that become:

• Less stable

• More soluble as cation size increases

What are key applications and properties of beryllium (Be)?

• Very strong and corrosion-resistant

• High melting point

• Toxic in powdered form

• Used in X-ray tubes (transparent to X-rays)

• Found in beryl, used for fake gems

What makes magnesium (Mg) valuable as a material?

• Strong and lightweight

• Flammable in fine form

• Used in structural alloys

• Found in chlorophyll in plants

What are common uses and biological roles of calcium (Ca)?

• Reacts with air to form calcium oxide (CaO)

• Found in bones and teeth

• Essential for muscle contraction

What are some applications of strontium (Sr)?

• Used in luminescent paints

• Found in Sensodyne toothpaste (helps reduce tooth sensitivity)

What is a key use of barium (Ba)?

• Reacts with air components

• Used to remove air from vacuum tubes

What are historical or niche uses of radium (Ra)?

• Used in radioluminous paints for glow-in-the-dark applications

• Now largely discontinued due to radioactivity