- Group 2 elements (alkaline earth metals)
- Reactivity towards air and water
- Group 2 elements: beryllium, magnesium, calcium, strontium, barium, and radium
- Alkaline earth metals have two valence electrons
- Have a tendency to lose these electrons to form a +2 cation
- Outer electron configuration: ns2 (n represents the principal quantum number)
- Reactivity with air:
- Beryllium: Forms an oxide layer on its surface, preventing further reaction
- Magnesium: Forms a protective layer of magnesium oxide (MgO)
- Calcium, strontium, barium: React with oxygen to form white metal oxides
- Radium: Extremely radioactive and reacts violently with air, forming oxides
- Reactivity with water:
- Beryllium: Does not react with water
- Magnesium: Reacts very slowly with cold water, releasing hydrogen gas
- Calcium: Reacts vigorously with cold water, producing calcium hydroxide and hydrogen gas
- Strontium, barium, radium: React very vigorously with water, releasing hydrogen gas
- Equation for the reaction of calcium with water:
- Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
- Reactivity Towards Air:
- Beryllium: Forms an oxide layer on its surface, preventing further reaction
- Magnesium: Forms a protective layer of magnesium oxide (MgO)
- Calcium: Reacts with oxygen to form calcium oxide (CaO)
- Strontium: Reacts with oxygen to form strontium oxide (SrO)
- Barium: Reacts with oxygen to form barium oxide (BaO)
- Radium: Extremely radioactive and reacts violently with air, forming oxides.
- Equation for the Reaction of Magnesium with Air:
- 2Mg(s) + O2(g) → 2MgO(s)
- Magnesium reacts with oxygen to form magnesium oxide.
- Equation for the Reaction of Calcium with Air:
- 2Ca(s) + O2(g) → 2CaO(s)
- Calcium reacts with oxygen to form calcium oxide.
- Equation for the Reaction of Strontium with Air:
- 2Sr(s) + O2(g) → 2SrO(s)
- Strontium reacts with oxygen to form strontium oxide.
- Equation for the Reaction of Barium with Air:
- 2Ba(s) + O2(g) → 2BaO(s)
- Barium reacts with oxygen to form barium oxide.
- Reactivity Towards Water:
- Beryllium: Does not react with water
- Magnesium: Reacts slowly with cold water, releasing hydrogen gas
- Calcium: Reacts vigorously with cold water, producing calcium hydroxide and hydrogen gas
- Strontium: Reacts very vigorously with water, releasing hydrogen gas
- Barium: Reacts very vigorously with water, releasing hydrogen gas
- Radium: Reacts violently with water, forming hydroxides and releasing hydrogen gas.
- Equation for the Reaction of Magnesium with Water:
- Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)
- Magnesium reacts with water to form magnesium hydroxide and hydrogen gas.
- Equation for the Reaction of Calcium with Water:
- Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
- Calcium reacts with water to form calcium hydroxide and hydrogen gas.
- Equation for the Reaction of Strontium with Water:
- Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g)
- Strontium reacts with water to form strontium hydroxide and hydrogen gas.
- Equation for the Reaction of Barium with Water:
- Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)
- Barium reacts with water to form barium hydroxide and hydrogen gas.
Slide 21:
- Properties of Group 2 Elements
- Alkaline earth metals
- Silvery-white in color
- High melting and boiling points
- High electrical and thermal conductivity
- Alkaline earth metals
- General trends across the group:
- Atomic and ionic radii increase down the group
- Ionization energy decreases down the group
- Electronegativity decreases down the group
Slide 22:
- Reaction of Group 2 Elements with Non-Metals
- Reactivity increases down the group
- Magnesium reacts with nitrogen to form magnesium nitride (Mg3N2)
- Calcium reacts with oxygen to form calcium oxide (CaO)
- Barium reacts with chlorine to form barium chloride (BaCl2)
- Radium reacts with fluorine to form radium fluoride (RaF2)
- These reactions are highly exothermic
Slide 23:
- Reaction of Group 2 Elements with Acids
- Alkaline earth metals react with acids to produce hydrogen gas
- Magnesium reacts with hydrochloric acid (HCl)
- Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
- Calcium reacts with sulfuric acid (H2SO4)
- Ca(s) + H2SO4(aq) → CaSO4(aq) + H2(g)
- Barium reacts with nitric acid (HNO3)
- Ba(s) + 2HNO3(aq) → Ba(NO3)2(aq) + H2(g)
Slide 24:
- Reaction of Group 2 Elements with Oxygen
- Alkaline earth metals react with oxygen to form metal oxides
- Beryllium forms beryllium oxide (BeO)
- Magnesium forms magnesium oxide (MgO)
- Calcium forms calcium oxide (CaO)
- Strontium forms strontium oxide (SrO)
- Barium forms barium oxide (BaO)
- Radium forms radium oxide (RaO)
Slide 25:
- Uses of Alkaline Earth Metals
- Magnesium:
- Used in the production of lightweight alloys for aerospace and automotive industries
- Used in fireworks, flares, and pyrotechnics
- Calcium:
- Essential for the growth and development of bones and teeth
- Used as a calcium supplement in medicine
- Barium:
- Used in X-ray imaging of the gastrointestinal tract
- Used in fireworks to produce green color
- Magnesium:
Slide 26:
- Summary of Group 2 Elements Reactivity
- Reactivity with air: Increases down the group
- Reactivity with water: Increases down the group
- Reactivity with non-metals: Increases down the group
- Reactivity with acids: Increases down the group
- Uses of alkaline earth metals: Vary based on the specific metal
Slide 27:
- Important equations:
- Reaction of magnesium with nitrogen:
- 3Mg(s) + N2(g) → Mg3N2(s)
- Reaction of calcium with oxygen:
- 2Ca(s) + O2(g) → 2CaO(s)
- Reaction of barium with chlorine:
- Ba(s) + Cl2(g) → BaCl2(s)
- Reaction of radium with fluorine:
- Ra(s) + F2(g) → RaF2(s)
- Reaction of magnesium with nitrogen:
Slide 28:
- Key points to remember:
- Group 2 elements are alkaline earth metals
- Reactivity towards air increases down the group
- Reactivity towards water increases down the group
- Group 2 elements react with non-metals and acids
- Important equations for reactions with nitrogen, oxygen, chlorine, and fluorine
Slide 29:
- Sample question:
- Which group 2 element reacts most vigorously with water? Explain the trend.
- Answer: The group 2 element that reacts most vigorously with water is barium. This is because reactivity with water increases down the group, and barium is located at the bottom of group 2.
Slide 30:
- References:
- Textbook: “Chemistry for 12th Boards” by XYZ
- Online resources:
Group 2 elements (alkaline earth metals) Reactivity towards air and water Group 2 elements: beryllium, magnesium, calcium, strontium, barium, and radium Alkaline earth metals have two valence electrons Have a tendency to lose these electrons to form a +2 cation Outer electron configuration: ns2 (n represents the principal quantum number) Reactivity with air: Beryllium: Forms an oxide layer on its surface, preventing further reaction Magnesium: Forms a protective layer of magnesium oxide (MgO) Calcium, strontium, barium: React with oxygen to form white metal oxides Radium: Extremely radioactive and reacts violently with air, forming oxides Reactivity with water: Beryllium: Does not react with water Magnesium: Reacts very slowly with cold water, releasing hydrogen gas Calcium: Reacts vigorously with cold water, producing calcium hydroxide and hydrogen gas Strontium, barium, radium: React very vigorously with water, releasing hydrogen gas Equation for the reaction of calcium with water: Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)