2.2: Group 2, the alkaline earth metals

What is the trend in atomic radius going down group 2?

• Increases down the group

• Extra shells are being added so the size of the molecule is increasing

What is the trend in first ionisation energy going down group 2?

• Decreases down the group

• Nuclear charge increases

• Shielding and atomic radius increases

• Electrostatic attraction decreases

• So less energy required to remove outer electron

What is the trend in melting/boiling point going down group 2?

• Decreases going down the group

• Atomic radius and size of molecule increases

• Shielding increases

• Metallic bonds are weaker

• So less energy required to break bonds

How reactive are the or group 2 metals with water?

• Mg: only reacts with steam

• Ca: vigorously reacts

• Sr: vigorously reacts

• Ba: vigorously reacts

What are the equations for group 2 metals with water?

• Mg(s) + H₂O(g) → MgO(s) + H₂(g)

• Ca(s) + 2H₂O(l) → Ca(OH)₂(s) + H₂(g)

• Sr(s) + 2H₂O(l) → Sr(OH)₂(s) + H₂(g)

• Ba(s) + 2H₂O(l) → Ba(OH)₂(s) + H₂(g)

What is the trend in solubility of metal hydroxides going down group 2?

• Increases going down the group

• Mg(OH)₂ is sparingly soluble

• Ba(OH)₂ is soluble

What is the trend in solubility of metal sulfates going down group 2?

Decreases going down the group

What is the equation for group 2 hydroxides being dissolved?

X(OH)₂ (aq) → X²⁺ (aq) + 2OH^- (aq)

What is the equation for group 2 sulfates being dissolved?

XSO₄ (s) → X²⁺ (aq) + 2SO₄^2- (aq)

What is Mg used for, and what is its equation?

• Extracting titanium from its core

• 2Mg + TiCl₄ → 2MgCl₂ + Ti

What is Mg(OH)₂ used for, and what is its equation?

• Neutralising stomach acid and treating constipation

• Mg(OH)₂ (s) + 2HCL(aq) → MgCl2 (aq) + 2H₂O (l)

What is Ca(OH)₂ used for?

raising pH of soil

What is CaO/CaCO₃ used for, and what is its equation?

sulfur scrubbing

What is BaSO₄ used for?

Barium meal that absorbs X-Rays

What is BaCl₂ used for?

• Testing for sulfate ions

• Produces a white ppt

• Acidified to remove any carbonates that may be present and produce a ppt