When we look at the transition from ammonia (NH3) to phosphine (BiH3), we can analyze the properties of these hydrides to determine which statement is incorrect. Let's break down each option to see how they relate to the trend in hydrides as we move down the group in the periodic table.
Understanding the Properties of Hydrides
Hydrides are compounds formed between hydrogen and other elements. As we move from NH3 to BiH3, we notice several trends that can help us evaluate the statements provided.
Statement Analysis
- a) The hydrides become increasingly difficult to prepare: This statement is generally correct. As we move down the group from nitrogen to bismuth, the bond strength between hydrogen and the central atom decreases. This makes it more challenging to synthesize these hydrides due to weaker interactions.
- b) The reducing power of the hydrides increases: This statement is also accurate. The reducing power of hydrides tends to increase down the group. For example, while NH3 is a weak reducing agent, BiH3 is a stronger reducing agent due to the larger size and lower electronegativity of bismuth compared to nitrogen.
- c) Their stability decreases: This statement is true as well. The stability of the hydrides decreases down the group. NH3 is quite stable, while BiH3 is less stable and more reactive, primarily due to the larger atomic size and lower bond strength.
- d) The ease of replacing hydrogen of the hydrides by other groups increases: This statement is the one that does not hold true. As we move down the group, the ability to replace hydrogen with other groups does not necessarily increase. In fact, the larger size and lower electronegativity of the heavier hydrides make them less reactive in terms of substitution reactions compared to their lighter counterparts.
Conclusion
Based on the analysis, the statement that is not correct is option d: "The ease of replacing hydrogen of the hydrides by other groups increases." As we progress from NH3 to BiH3, the hydrides exhibit decreasing stability and reactivity, which affects their ability to undergo substitution reactions. Thus, this statement stands out as the incorrect one in the context of hydride chemistry.
