Question

Which of the following statements is not correct? (1) Affinity for oxygen to form basic oxides increases in the order \(\mathrm{BeO}<\mathrm{MgO}<\mathrm{CaO}<\mathrm{SrO}<\mathrm{BaO}\) (2) Basic strength of oxides and hydroxides increases from Be to Ba compounds. (3) Bicarbonates of alkaline earth metals do not exist in solid state but they are known in solutions. (4) A1l are correct.

Short answer

Statement (4) is not correct as it suggests none of the above statements are correct while they all are.

Step-by-step solution

- Understand the Statements

Read each statement carefully to understand their meaning and concepts. These involve properties of alkaline earth metals and their oxides and hydroxides.

- Check Affinity for Oxygen

Statement (1): Check if it is true that the affinity for oxygen to form basic oxides increases in the order \( \mathrm{BeO}<\mathrm{MgO}<\mathrm{CaO}<\mathrm{SrO}<\mathrm{BaO} \). Alkaline earth metals’ ability to form basic oxides increases down the group due to increasing atomic size and decreasing ionization energy.

- Verify the Basic Strength

Statement (2): Verify if the basic strength of oxides and hydroxides increases from Be to Ba compounds. This is true as basicity increases with increasing atomic size and decreasing electronegativity.

- Check Existence of Bicarbonates

Statement (3): Examine if bicarbonates of alkaline earth metals do not exist in solid state but are known in solutions. Bicarbonates are only stable in aqueous solutions and do not form stable solid bicarbonates. This statement is correct.

- Conclusion

All three statements (1), (2), and (3) are correct.

Key concepts

Basic Oxides

Alkaline earth metals form basic oxides, which are compounds consisting of a metal and oxygen. The term 'basic' refers to their tendency to react with acids to form salts and water. The formation of these basic oxides becomes more favorable as we move down the group in the periodic table.
Here's why:

• The atomic size increases, which makes it easier for the metal to react with oxygen.
• There is a decrease in ionization energy, which means the metal atoms more readily give up their electrons to bond with oxygen.

As a result, the ability to form basic oxides increases in the order: \[ \text{BeO} < \text{MgO} < \text{CaO} < \text{SrO} < \text{BaO} \] This pattern reflects the increasing reactivity of the metals as we proceed from beryllium (Be) to barium (Ba).

Basic Strength

The 'basic strength' of an oxide or hydroxide refers to its ability to neutralize acids. For alkaline earth metals, this strength increases from beryllium (Be) to barium (Ba). This happens because:

• The size of the metal ions increases, which makes it easier for them to release hydroxide ions (OH^-).
• The electronegativity decreases, causing the metal oxid/e\to dissociate more readily into ions.

Therefore, oxides and hydroxides of heavier alkaline earth metals (like barium and strontium) are more basic compared to those of lighter ones (like beryllium and magnesium). This trend is evident in their reactions with acids. For instance, barium hydroxide (\text{Ba(OH)\(_2\)}) shows stronger basic properties than magnesium hydroxide (\text{Mg(OH)\(_2\)}]).

Bicarbonates in Solution

Bicarbonates are an interesting aspect of alkaline earth metals. These compounds generally exist only in aqueous solutions and not in solid forms. Here's why that happens:

• Bicarbonates are unstable in solid form and tend to decompose into carbonates and water when isolated.
• In solution, they stay stable because the water molecules help to maintain their structure through hydrogen bonding.

When you dissolve an alkaline earth metal bicarbonate in water, it stays dissolved and can be part of various chemical reactions. For example, calcium bicarbonate, commonly found in hard water, exists as \text{Ca(HCO\(_3\))\(_2\)} in solution. However, if you try to isolate it as a solid, it quickly decomposes into calcium carbonate (\text{CaCO\(3\)}) and releases carbon dioxide (\text{CO\(2\)}).