Question

Which of the following about compounds of lithium is false? (1) The hydroxide, carbonatc and nitrate decompose to give the oxide on heating. (2) It is the most clectroncgative clement of group I \(\Lambda\). (3) The hydrogen carbonate can be isolated in stable state. (4) It forms an oxidc but not a supcroxide.

Short answer

Option 2 is false.

Step-by-step solution

- Understand the given options

First, read through all the given statements about compounds of lithium and ensure each term is understood: hydroxide, carbonate, nitrate, hydrogen carbonate, oxide, superoxide, and electronegativity.

- Evaluate option 1

Check if lithium hydroxide, carbonate, and nitrate decompose to form lithium oxide upon heating. According to chemical properties, lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3) do decompose to give lithium oxide (Li2O) when heated.

- Evaluate option 2

Verify the electronegativity of lithium relative to other group I elements. Lithium is actually the least electronegative element in group I (Alkali metals), not the most.

- Evaluate option 3

Check if lithium hydrogen carbonate (LiHCO3) can exist in a stable state. Yes, lithium hydrogen carbonate can be isolated and is stable.

- Evaluate option 4

Determine if lithium forms an oxide (Li2O) but not a superoxide. Lithium indeed forms an oxide, but it does not form a superoxide.

- Identify the false statement

Based on the evaluation of each option, identify which statement about compounds of lithium is incorrect. Option 2 is the false statement because lithium is the least electronegative element in group I, not the most.

Key concepts

lithium properties

Lithium is the lightest metal and belongs to the Alkali metal group in the periodic table. This group is also known as Group I elements. Lithium exhibits distinct characteristics:
• It has a low density and is soft and silvery-white in appearance.
• It is highly reactive, especially in the presence of water and air. To prevent reaction with air, it is often stored in oil.
• Lithium forms a variety of compounds such as hydroxides, carbonates, nitrates, and oxides. When lithium compounds decompose under heat, they often produce lithium oxide.

electronegativity in Group I elements

Electronegativity is a measure of an atom's ability to attract and hold onto electrons. Among Group I elements, lithium has the highest electronegativity, but it is still relatively low compared to other elements in the periodic table. However, contrary to what one might think, within Group I, electronegativity decreases as you move down the group:
• Lithium (Li) has the highest electronegativity in Group I with a value of approximately 0.98.
• Sodium (Na) follows with a lower electronegativity.
• Potassium (K), Rubidium (Rb), and Cesium (Cs) continue this trend with progressively lower values.

Electronegativity trends in Group I are crucial in understanding the reactivity and bonding behaviors of these metals. Lithium's relatively higher electronegativity also contributes to its unique chemical behavior compared to its heavier congeners.

thermal decomposition of lithium compounds

Thermal decomposition refers to the process in which a chemical compound breaks down into simpler substances when heated. Lithium compounds such as hydroxides, carbonates, and nitrates undergo thermal decomposition to produce lithium oxide (Li2O). Here's how this process looks for some compounds:
• Lithium hydroxide (LiOH) decomposes upon heating to form lithium oxide (Li2O) and water (H2O): \[ 2LiOH \rightarrow Li2O + H2O \]
• Lithium carbonate (Li2CO3) decomposes to yield lithium oxide (Li2O) and carbon dioxide (CO2): \[ Li2CO3 \rightarrow Li2O + CO2 \]
• Lithium nitrate (LiNO3) breaks down to produce lithium oxide (Li2O), nitrogen dioxide (NO2), and oxygen (O2): \[ 4LiNO3 \rightarrow 2Li2O + 4NO2 + O2 \]
Understanding these reactions helps in predicting the products formed when lithium compounds are heated. This knowledge is particularly useful in fields where thermal stability and decomposition products are critical, such as materials science and chemical engineering.