Question

Read the given passage and answer the questions that follow:

When an electron is added to a neutral gaseous atom (X) to convert it into a negative ion, the enthalpy change accompanying the process is defined as the Electron Gain Enthalpy (∆egH). Electron gain enthalpy provides a measure of the ease with which an atom adds an electron to form anion as represented by equation X(g) + e – → X – (g) . Depending on the element, the process of adding an electron to the atom can be either endothermic or exothermic....

1. The first electron gain enthalpy values are positive for the noble gases. Why?


2. (i)The first electron gain enthalpy values for the 3rd period elements in the P block is more than the respective
(ii) period elements, why?

3. Second electron gain enthalpy is generally negative, why?

4. What is the trend in electron affinity along the period and group?

5. Electron gain enthalpy of F is lower than the Cl while the I.E value is higher. Explain​

Answer 1

Answer:

Explanation:

1. The noble gases present in the group 18 of periodic table, have electronic configuration ns2np6. . Thus, in case of noble gases, where it resists the addition of electrons, extra energy is required in order to force the electron to bind to the stable atom. Therefore, making the electron gain enthalpies positive.  

2. (i) hlorine has one more electron shell than fluorine, resulting in a greater shielding effect ie how much the other electrons repel in the incoming electron. So since chlorine gas more electrons contributing to the repulsion, more so than fluorine, more energy is required to cause an electron to be added to chlorine than fluorine.