chapter 9: group 2 alkaline earth metals

why are group 2 elements called the alkaline earth metals

their oxides and hydroxides are alkaline and form alkaline solutions

why is beryllium not considered in most general trends

it is not a typical group 2 element because Beryllium’s small size, covalent bonding nature, and limited reactivity make it an anomaly in Group 2, so it is not considered in most general trends to avoid confusion and provide clearer explanations for the rest of the group’s behavior.

physical properties of group 2 to remember

• electron arrangement

• the sizesof atoms

• melting points

• ionisation energies

electron arrangement

2 electrons in the outer s orbital

general trend in melting point for group 2

• melting point decreases going down

• strength of metallic bonds decreases

• because the electrons get farther away from the positive nuclei

anomaly: magnesium has the lowest

ionisation energy general trend group 2

• ionisation energy decreases going down

• more shielding

• greater distance from positive nuclei to valence shell electron

symbol equation for decomposition of limestone

CaCO3(s)→ CaO(s) + CO2(g)

uses of calcium oxide and hydroxide

neutralises acids in soil

calcium oxide + hydrochloric acid

CaO(s) +2HCl → CaCl2(aq) → CaCl2 (aq) + H2O (l)

calcium hydroxide + hydrochloric acid

Ca(OH)2 +2HCl(aq) → CaCl2 (aq) + 2H2O (l)

what happens to group 2 elements in chemical reactions

• they go through oxidation

• oxidation state 0 to 2+

general trend when they react with water

• get more reactive going down

• M(s) +2H2O(l) → M(OH)2 + H2

magnesium hydroxide

• milk of magnesia

• neutralises excess stomach acid

magnesium + steam

Mg(s) + H2O(g) → MgO (s) + H2(g)

magnesium + cold water

Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)

Ca + water symbol equation

Ca (s) + 2H2O(l) → Ca(OH)2 (aq)+ H2 (l)

calcium hydroxide uses

• aka slaked lime

• treats acidic soils

• keeps the soil at an optimum PH

general trend in solubilities of metal hydroxides

• going down they get more soluble

• white solids formed

metal hydroxide features of solubility

Mg(OH)2 = insoluble

Ca(OH)2 = sparingly soluble used as limewater

Sr(OH)2 = more soluble

Ba(OH)2 = dissolves to produce a strongly alkaline solution

general trend in solubilities of group 2 metal sulfates

• going down get less soluble

barium sulfate

• used a barium meal

• outlines the gut in medical x-rays

• barium compounds are highly toxic

• this test is safe because barium sulfate is insoluble

test for sulfate ions

• add hydrochloric acid

• add barium sulfate

• barium chloride is formed and added to the solution if sulfate ions are present

• white precipitate

flue gas

mixture of gases formed when fossil fuels are burned

why is flue gas bad

contains sulfur / sulfur dioxide which damage the environment and contributes to acid rain

how is sulfur removed from flue gas

flue gases get passed through a suspension of calcium oxide

reacts to form calcium sulfate aka gypsum

equations for flue gas desulfurisation

CaO(s) + SO2(g) → CaSO3 (s)

CaCO3(s) + SO2(g) → CaSO3(s) +CO2(g)

why is titanium extracted

• high melting point

• low density

• strong

uses of titanium

aurospace industry

how is titanium extracted from its metal oxide

titanium oxide + chlorine + carbon → titanium chloride and carbon monoxide

equaion for the reduction of titanium chloride with magnesium

TiCl4 (l) + 2Mg(s) → 2MgCl2(s) + Ti(s)