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(b) Electron Affinity Is the Heat Energy Change When One Mole of Gaseous Atoms Gains One Mole of Electrons. Table 1 Shows the Equations

Question

(b) Electron affinity is the heat energy change when one mole of gaseous atoms gains one mole of electrons. Table 1 shows the equations and the energy change for the first two electron affinities of oxygen. cline ( 2 - 3 ) multicolumn(1)(c|){} & equation & energy change first electron affinity & mathrm(O)(mathrm(g))+mathrm(e)^- arrow mathrm(O)^-(mathrm(g)) & releases energy second electron affinity & mathrm(O)^-(mathrm(g))+mathrm(e)^- arrow mathrm(O)^2-(mathrm(g)) & requires energy Table 1 Explain why the first electron affinity of oxygen releases energy but the second electron affinity of oxygen requires energy. (3) (Total for Question 3=6 marks)

Answer

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Yael Master · Tutor for 5 years

Answer

The first electron affinity of oxygen releases energy because the added electron is attracted to the positively charged nucleus, resulting in a release of energy. The second electron affinity of oxygen requires energy because the added electron is repelled by the negatively charged oxygen ion, requiring an input of energy to overcome this repulsion.

Explanation

## Step 1: Understanding Electron AffinityElectron affinity is the energy change that occurs when an atom or ion in the gaseous state gains an electron. The first electron affinity refers to the energy change when a neutral atom gains an electron, while the second electron affinity refers to the energy change when a negatively charged ion gains an additional electron.## Step 2: First Electron Affinity of OxygenThe first electron affinity of oxygen is exothermic, meaning it releases energy. This is because the electron being added is attracted to the positively charged nucleus of the oxygen atom. The electron is added to a relatively low energy level close to the nucleus, and this process releases energy.### The equation for this process is: \( \mathrm{O}(g) + \mathrm{e}^{-} \rightarrow \mathrm{O}^{-}(g) \)## Step 3: Second Electron Affinity of OxygenThe second electron affinity of oxygen is endothermic, meaning it requires energy. This is because the electron being added is repelled by the negatively charged oxygen ion, \( \mathrm{O}^{-}(g) \). The electron is added to a higher energy level further from the nucleus, and this process requires an input of energy to overcome the repulsion between the negatively charged ion and the incoming electron.### The equation for this process is: \( \mathrm{O}^{-}(g) + \mathrm{e}^{-} \rightarrow \mathrm{O}^{2-}(g) \)