Question

Which of the following statements is correct? (1) No peroxide of beryllium is known is on date. (2) The ease with which peroxide is formed decreases with increase in the size of atom. (3) \(\mathrm{BaO}_{2}\) is prepared by passing air over \(\mathrm{BaO}\) at \(500^{\circ} \mathrm{C}\) (4) Peroxide of \(\mathrm{Mg}, \mathrm{Ca}, \mathrm{Sr}\) and \(\mathrm{Ba}\) are white ionic solids containing \(\mathbf{O}_{2}^{2-}\) ion.

Short answer

Statements (1), (3), and (4) are correct.

Step-by-step solution

Evaluate Statement (1)

Verify the statement 'No peroxide of beryllium is known is on date.' By current knowledge, this statement is correct as beryllium does not readily form peroxides.

Evaluate Statement (2)

Assess the statement 'The ease with which peroxide is formed decreases with increase in the size of atom.' This statement is false because as the size of the atom increases down the group in the periodic table, the ease of peroxide formation increases.

Evaluate Statement (3)

Examine the given information 'BaO2 is prepared by passing air over BaO at 500°C.' This statement is correct as this is a known method of preparing barium peroxide.

Evaluate Statement (4)

Check the correctness of 'Peroxide of Mg, Ca, Sr and Ba are white ionic solids containing O2^2- ion.' This statement is true as it correctly describes the nature of these peroxides.

Conclusion

After verifying each statement individually, statements (1), (3), and (4) are correct, while statement (2) is incorrect.

Key concepts

Group 2 Elements

Group 2 elements, also known as the alkaline earth metals, include beryllium, magnesium, calcium, strontium, barium, and radium. These elements are located in the second column of the periodic table and share several key characteristics.

• They possess two electrons in their outermost energy level.
• These metals are highly reactive, although less so than group 1 elements.
• They form ionic compounds by losing their two valence electrons to acquire a +2 oxidation state.

Understanding the properties of these elements is essential for grasping their chemical behavior, including the formation of peroxides.

Peroxide Formation

Peroxide formation is a specific type of chemical reaction where an element combines with oxygen to form a peroxide compound.

• In the case of Group 2 elements, peroxides have the general formula MO₂, where M represents an element from this group.
• These peroxides contain the peroxide ion, \(O_2^{2-} \), which is a distinctive feature.
• The ability to form peroxides increases as you move down the group from beryllium to barium.

For instance, beryllium does not readily form peroxides due to its smaller atomic size and high ionization energy, while barium readily forms barium peroxide (\(BaO_2\)), demonstrating how the formation becomes easier for larger atoms. This trend is crucial for predicting the chemical behavior of these metals.

Chemical Reactions of Barium

Barium, one of the heavier Group 2 elements, exhibits unique chemical behavior.

• One notable reaction is the formation of barium peroxide (\(BaO_2\)), which can be synthesized by passing air or oxygen over barium oxide (BaO) at high temperatures around 500°C.
• The reaction is: \[2BaO + O_2 \rightarrow 2BaO_2 \]
• Barium, like other Group 2 elements, forms largely ionic compounds.

This oxidation process highlights the reactive nature of barium and its ability to form a peroxide, a compound characterized by the oxygen-oxygen single bond. Understanding the chemical reactions of barium provides insights into how alkaline earth metals react with other elements.

Ionic Solids

Ionic solids are a type of crystalline solid where ions are held together by electrostatic forces, which are strong and predominate in compounds formed by Group 2 elements.

• Peroxides of magnesium, calcium, strontium, and barium are examples of such ionic solids with the general formula MO₂.
• These solids are characterized by the presence of the peroxide ion (\(O_2^{2-} \)).
• They typically appear as white solids due to the efficient packing of ions in a crystal lattice.

The properties of these ionic solids, such as high melting points, hardness, and electrical conductivity in the molten state, are direct results of the strong ionic bonds. Recognizing these characteristics can aid in understanding the physical and chemical properties of ionic compounds formed by Group 2 elements.