Group II Elements (Alkaline Earth Metals) Flashcards

Vocabulary flashcards reviewing Group II trends, physical properties, chemical reactions, and thermal stability.

Alkaline Earth Metals

Group II elements whose oxides react with water to form an alkaline solution.

s-Block Elements (Group II)

The classification given to Group II elements because their outer shell electrons reside in the s-subshell.

Atomic Radii Trend in Group II

Increases down the group because atomic number, proton number, electron number, and the number of principal quantum shells increase, expanding the distance of the outer shell from the nucleus.

Ionic Radii Trend in Group II

Increases down Group II but remains smaller than metallic radii because forming $M^{2+}$ ions requires removing $2e^-$ from the outer shell, eliminating the outer shell entirely and reducing nuclear distance.

Ionization Energy Trend in Group II

Decreases down the group because increased nuclear charge, outer shell distance, and shielding effect reduce the attraction between protons and outer electrons, making electrons easier to remove.

Refractory Material

A substance that does not decompose or melt at high temperatures, such as magnesium oxide ($\text{MgO}$), which possesses a giant ionic lattice and high melting and boiling points.

Solubility and pH Trend of Group II Hydroxides

Increases down the group, making $\text{Be(OH)}_2$ the least soluble hydroxide with a relatively low pH and $\text{Ba(OH)}_2$ the most soluble hydroxide with the highest pH value.

Solubility Trend of Group II Sulphates

Decreases down the group, making $\text{BeSO}_4$ the most soluble sulphate and $\text{BaSO}_4$ the least soluble sulphate.

Flame Test Observation for Calcium Reaction with Oxygen

Forms a white solid ($\text{CaO}$) and burns with a brick red flame according to $2\text{Ca}(s) + \text{O}_2(g) \rightarrow 2\text{CaO}(s)$.

Flame Test Observation for Barium Reaction with Oxygen

Forms a white solid ($\text{BaO}$) and burns with an apple green flame according to $2\text{Ba}(s) + \text{O}_2(g) \rightarrow 2\text{BaO}(s)$.

Reaction of Magnesium with Steam

A vigorous reaction that produces a white solid ($\text{MgO}$) and evolves a colourless gas ($\text{H}_2$) that makes a pop sound with a lighted splint according to $\text{Mg}(s) + \text{H}_2\text{O}(g) \rightarrow \text{MgO}(s) + \text{H}_2(g)$.

Thermal Decomposition of Group II Carbonates

An endothermic process ($\Delta H = \text{+ve}\text{ kJ\,mol}^{-1}$) where heat is absorbed to decompose metal carbonates into metal oxides and carbon dioxide gas according to $\text{MCO}_3(s) \rightarrow \text{MO}(s) + \text{CO}_2(g)$.

Thermal Decomposition Temperature of $\text{MgCO}_3$ vs. $\text{BaCO}_3$

$\text{MgCO}_3$ decomposes at $540\,^\circ\text{C}$, whereas $\text{BaCO}_3$ decomposes at $1360\,^\circ\text{C}$, demonstrating that thermal stability increases down Group II.

Thermal Decomposition of Group II Nitrates

Thermal breakdown upon heating to form metal oxide, brown nitrogen dioxide gas ($\text{NO}_2$), and oxygen gas according to $2\text{M(NO}_3)_2(s) \rightarrow 2\text{MO}(s) + 4\text{NO}_2(g) + \text{O}_2(g)$.

Effect of Insoluble Sulphate Formation on Reaction Rate

When Group II oxides, metals, or hydroxides react with dilute $\text{H}_2\text{SO}_4$, an insoluble sulphate precipitate layer forms on the surface, preventing acid molecules from colliding with the reactant and slowing the reaction rate.