Which reaction below represents the electron affinity of Li?
Li(g)+e-→ Li(g) .
Li(g) → Li+(g) + e-
Li(g)e-→ Li+(g)
Li+(g)→ Li(g)+ e-
Li+(g)+ e-→ Li(g)
The Correct Answer and Explanation is :
The correct reaction representing the electron affinity of lithium (Li) is:
Li⁺(g) + e⁻ → Li(g)
Explanation:
Electron affinity refers to the amount of energy released or absorbed when an electron is added to a neutral atom in the gas phase to form a negatively charged ion. In simpler terms, it’s the energy change when an electron is gained by an atom.
For lithium (Li), the electron affinity specifically refers to the process of adding an electron to the positively charged lithium ion (Li⁺) to form a neutral lithium atom (Li). The equation is:
Li⁺(g) + e⁻ → Li(g)
Here’s why this is the correct representation:
- Li(g) + e⁻ → Li⁻(g): This would be the process of adding an electron to a neutral lithium atom to form a negative ion (Li⁻), which would represent electron attachment, not electron affinity. This process requires energy input, and thus it does not represent electron affinity, which is typically exothermic (releases energy).
- Li(g) → Li⁺(g) + e⁻: This represents ionization, where lithium loses an electron to form a cation (Li⁺). This is the opposite of electron affinity because it involves removing an electron, not adding one.
- Li(g) + e⁻ → Li(g): This is simply the neutral lithium atom with no change, so it doesn’t represent electron affinity either.
- Li⁺(g) → Li(g) + e⁻: This is the reverse of ionization, where a lithium ion (Li⁺) would release an electron to form a neutral atom. It’s not related to the concept of electron affinity, which is the addition of an electron, not the removal of one.
Therefore, the process Li⁺(g) + e⁻ → Li(g) correctly describes the electron affinity of lithium, as it shows the release of energy when an electron is added to a lithium ion to form a neutral atom.