Group 2 Elements Chemistry Notes

Group 2 Metals ### Reactions with Oxygen - Group 2 metals generally burn in oxygen to form metal oxides. -

Beryllium (Be):

• Coated in a thin layer of beryllium oxide (BeO), which inhibits the reaction.

• Reacts only in powder form.

• Equation: 2Be + O_2 \rightarrow 2BeO

• Magnesium (Mg):

• Burns in oxygen with a bright white flame.

• Equation: 2Mg + O_2 \rightarrow 2MgO

• Calcium (Ca):

• Burns with a bright white flame that is slightly red at the top.

• Equation: 2Ca + O_2 \rightarrow 2CaO

• Strontium (Sr):

• Reluctant to start burning but burns intensely with a white flame.

• Equation: 2Sr + O_2 \rightarrow 2SrO

• Barium (Ba):

• Burns in oxygen with a white flame.

• Equation: 2Ba + O_2 \rightarrow 2BaO ### Reactions with Water - Reactions with water or steam show the trend in reactivity down the group. -
  Beryllium (Be):

• Reacts with steam only at very high temperatures.

• Equation: Be + H_2O \rightarrow BeO + H_2

• Magnesium (Mg):

• Very slight reaction with cold water.

• Reaction stops due to the production of an insoluble coat of magnesium hydroxide (Mg(OH)\2).

• Equation: Mg + 2H_2O \rightarrow Mg(OH)_2 + H_2

• Burns more readily in steam than in cold water.

• Equation: Mg + H_2O \rightarrow MgO + H_2

• Calcium (Ca), Strontium (Sr), and Barium (Ba):

• React in cold water to produce their hydroxide and hydrogen gas.

• Reactions become increasingly vigorous down the group.

• Example (Calcium): Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2

• Reactivity increases down Group 2, with barium reacting the fastest. ### Reactions with Dilute Acids - All Group 2 metals react with dilute hydrochloric acid (HCl) to produce a metal chloride and hydrogen gas.

• Reactions become more vigorous down the group.

• General Equation: X + 2HCl \rightarrow XCl_2 + H_2 (where X is a Group 2 metal).

• Dilute sulfuric acid (H_2SO_4) reacts with Group 2 metals to produce a metal sulfate and hydrogen.

• Reactions do not get more vigorous down the group due to the solubility of the sulfates produced.

• General Equation: X + H_2SO_4 \rightarrow XSO_4 + H_2 (where X is a Group 2 metal). ### Group 2 Oxides #### Reactions with Water - Apart from beryllium oxide (BeO), all Group 2 oxides react with water to produce hydroxides.

• General Equation: XO + H_2O \rightarrow X(OH)_2 #### Reactions with Dilute Acids - All Group 2 oxides react with dilute acids to produce salt and water.

• With Hydrochloric Acid: XO + 2HCl \rightarrow XCl_2 + H_2O

• With Nitric Acid: XO + 2HNO_3 \rightarrow X(NO_3)_2 + H_2O

• With Sulfuric Acid: XO + H_2SO_4 \rightarrow XSO_4 + H_2O ### Group 2 Hydroxides #### Reactions with Water - Group 2 hydroxides do not react with water. #### Reactions with Dilute Acids - Group 2 hydroxides react with dilute acids similarly to metal oxides, but produce two water molecules.

• Example: Sr(OH)_2 + 2HCl \rightarrow SrCl_2 + 2H_2O ### Metal Carbonates #### Reactions with Water - Group 2 metal carbonates are insoluble and do not react with water. #### Reactions with Dilute Acids - Group 2 carbonates react with dilute acids to produce a salt, water, and carbon dioxide.

• With Hydrochloric Acid: XCO_3 + 2HCl \rightarrow XCl_2 + H_2O + CO_2

• With Nitric Acid: XCO_3 + 2HNO_3 \rightarrow X(NO_3)_2 + H_2O + CO_2

• With Sulfuric Acid: XCO_3 + H_2SO_4 \rightarrow XSO_4 + H_2O + CO_2 ### Thermal Decomposition #### Nitrates - All Group 2 nitrates undergo thermal decomposition to produce a metal oxide, oxygen, and nitrogen dioxide.

• General Equation: 2X(NO_3)_2 \rightarrow 2XO + 4NO_2 + O_2

• Observations: Nitrate and oxide are white solids; nitrogen dioxide is a brown gas. #### Carbonates - All Group 2 carbonates undergo thermal decomposition to produce a metal oxide and carbon dioxide.

• General Equation: XCO_3 \rightarrow XO + CO_2

• Observations: Carbonate and oxide are white solids; carbon dioxide is a colorless gas.

• Both Group 2 carbonates and nitrates become more stable to heat as you go down the group, requiring stronger heating for thermal decomposition. ### Trends in Reactivity and Solubility - Generally, reactivity increases down Group 2. - Ionization energy decreases down the group due to increasing atomic radius and shielding effect, making electrons easier to remove. - Solubility:

• Hydroxides: Solubility increases down the group.

• Sulfates: Solubility decreases down the group. ### Uses of Group 2 Compounds - Calcium hydroxide (Ca(OH)\2) and calcium carbonate

calcium carbonate (CaCO3) are used to neutralize acidic soils in agriculture. - Magnesium hydroxide (Mg(OH)2) is used in antacids and laxatives. - Barium sulfate (BaSO_4) is used as a contrast agent in medical X-rays. ### Flame Colors - When heated in a flame, Group 2 compounds produce characteristic colors. - Magnesium: No flame color. - Calcium: Brick red flame. - Strontium: Red flame. - Barium: Green flame.