Question

Which of the following statements are correct? 
A. The process of the addition an electron to a neutral gaseous atom is always exothermic 
B. The process of removing an electron from an isolated gaseous atom is always endothermic 
C. The 1st ionization energy of the boron is less than that of the beryllium 
D. The electronegativity of C is 2.5 in $ CH_4 $ and $ CCl_4 $ 
E. Li is the most electropositive among elements of group 1 
Choose the correct answer from the options given below

• A. B and C only
• B. A, C and D only
• C. B and D only
• D. B, C and E only

Hint:

Review the definitions of electron affinity, ionization energy, electronegativity, and electropositivity. Consider the electronic configurations and trends in the periodic table.

Answer 1

The Correct Option is A

• [(A)] The process of adding an \( e^- \) to a neutral gaseous atom is not always exothermic; it may be exothermic or endothermic.
• [(B)] Be: 1s²2s² B: 1s²2s²2p¹
  In Be, the 2s subshell is fully filled.
  So, high energy is needed to remove an \( e^- \) as compared to B.
• [(D)] In \( CCl_4 \), due to partially positive charge, \( Z_{eff} \uparrow \) So, EN of C: \( CCl_4>CH_4 \)
• [(E)] Cs is most electropositive

Answer 2

To determine which of the given statements are correct, let's analyze each one:

1. Statement A: "The process of the addition of an electron to a neutral gaseous atom is always exothermic."
   • The addition of an electron to some atoms is exothermic because energy is released when an electron is added. However, this is not always the case. For example, noble gases such as Neon (Ne), or elements with stable electronic configurations, may require energy input, making the process endothermic.
   • Therefore, statement A is incorrect.
2. Statement B: "The process of removing an electron from an isolated gaseous atom is always endothermic."
   • Removing an electron from an isolated gaseous atom indeed requires energy to overcome the attraction between the negatively charged electron and the positively charged nucleus. This means the process is always endothermic.
   • Therefore, statement B is correct.
3. Statement C: "The 1st ionization energy of boron is less than that of beryllium."
   • Ionization energy is the energy required to remove the outermost electron. Boron (B) has a lower ionization energy compared to beryllium (Be) because B has a less stable electronic configuration compared to the filled s orbital of Be.
   • This makes the removal of the outer electron in boron easier than in beryllium.
   • Therefore, statement C is correct.
4. Statement D: "The electronegativity of C is 2.5 in CH₄ and CCl₄."
   • Electronegativity is a property of an element and does not change between different compounds. The value stated does not change whether carbon is in CH₄ or CCl₄.
   • Therefore, statement D is correct in terms of recognizing that the electronegativity of carbon is consistent in different compounds, though misinterpretation might occur if the context indicates something else.
5. Statement E: "Li is the most electropositive among elements of group 1."
   • Electropositivity increases down the group, meaning that elements become more electropositive than lithium (Li) as we move down Group 1. Thus, Fr is typically considered more electropositive than Li.
   • Therefore, statement E is incorrect.

Based on the analysis above, the correct statements are B and C. Thus, the correct answer is B and C only.