Question

The correct order regarding the solubility of alkaline carth metal halide in water is (1) \(\mathrm{BeCl}_{2}>\mathrm{MgCl}_{2}>\mathrm{CaCl}_{2}>\mathrm{SrCl}_{2}>\mathrm{BaC} \mathrm{l}_{2}\) (2) \(\mathrm{MgCl}_{2}>\mathrm{CaCl}_{2}>\mathrm{BeCl}_{2}>\mathrm{BaCl}_{2}>\mathrm{SrCl}_{2}\) (3) \(\mathrm{BaCl}_{2}>\mathrm{MgCl}_{2}>\mathrm{CaCl}_{2}>\mathrm{BeCl}_{2}>\mathrm{SrCl}_{2}\) (4) \(\mathrm{CaCl}_{2}>\mathrm{MgCl}_{2}>\mathrm{SrCl}_{2}>\mathrm{BaCl}_{2}>\mathrm{BeCl}_{2}\)

Short answer

(1) \(\mathrm{BeCl}_2 > \mathrm{MgCl}_2 > \mathrm{CaCl}_2 > \mathrm{SrCl}_2 > \mathrm{BaCl}_2\)

Step-by-step solution

Understand the Solubility Trends

The solubility of alkaline earth metal halides in water generally decreases as you move down the group in the periodic table. This is due to the increasing ionic size and decreasing lattice energy.

Analyze the Given Options

Examine each of the provided answer options to identify the one that follows the solubility trend identified in Step 1.

Match the Trend to the Options

The correct order should follow the decreasing solubility trend: (1) \(\mathrm{BeCl}_2 > \mathrm{MgCl}_2 > \mathrm{CaCl}_2 > \mathrm{SrCl}_2 > \mathrm{BaCl}_2\).

Key concepts

trends in periodic table

The periodic table exhibits various trends, one of which affects the solubility of alkaline earth metal halides. As you move down Group 2 of the periodic table, which includes Be, Mg, Ca, Sr, and Ba, several properties change predictably.
Here's a breakdown:

• Atomic and Ionic Size: The size of atoms and their corresponding ions increases from Be to Ba. The larger the ion, the more space it occupies and the weaker its interactions with other ions or molecules.
• Ionization Energy: The energy required to remove an electron decreases as you go down the group. Elements like Beryllium (Be) have higher ionization energies compared to Barium (Ba).
• Electronegativity: The ability of an atom to attract electrons drops as you proceed from Be to Ba. Higher elements in the group hold onto their electrons more tightly, making them less reactive in some contexts.

The understanding of these trends helps to predict the behavior of these elements and their compounds in various contexts, including solubility in water.

alkaline earth metals

Alkaline earth metals are found in Group 2 of the periodic table. These include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). Here's what you need to know about them:

• Outer Electron Configuration: All alkaline earth metals have two electrons in their outermost energy level. This makes them very reactive, although slightly less so than their Group 1 counterparts (alkali metals).
• Reactivity: Their reactivity increases down the group. Barium is more reactive than Calcium, which is more reactive than Magnesium, and so on.
• Formation of Compounds: These elements readily form halides (compounds with halogens like Cl, Br, etc.). The halides of these metals are typically ionic and crystalline in nature.

This group showcases diverse chemical properties that are invaluable in both industrial and everyday applications, such as in the formation of metals and salts.

lattice energy

Lattice energy is a critical concept in understanding the solubility of ionic compounds like alkaline earth metal halides. It refers to the energy required to separate one mole of an ionic solid into its gas-phase ions. Here's why it matters:

• Magnitude: Lattice energy is higher for ions with greater charge and smaller size. For example, BeCl₂ has higher lattice energy compared to BaCl₂ due to the smaller ionic radius of Be²⁺.
• Effect on Solubility: Higher lattice energy means stronger ionic bonds, making the compound less soluble in water. This explains why BeCl₂ is more soluble than BaCl₂.
• Lattice Energy and Periodic Trends: As you move down the group of alkaline earth metals, lattice energy decreases. This trend aligns with the increasing ionic size and stronger solubility properties in higher elements.

Understanding lattice energy helps in predicting and explaining the solubility trends observed in alkaline earth metal halides.