Which of the following statements is false? 
a) The electron affinity of phosphorus is less exothermic than those of both silicon and sulfur. 
b) The second ionization energy of oxygen is less than the first ionization of fluorine.
c) As the principal quantum number of an atom increases the effective nuclear charge will increase. 
d) Cations are smaller than their parent atoms. 
e) The second electron affinity of an atom will be more exothermic than the first electron affinity. 

• A. b only
• B. b and c
• C. a, c and e
• D. a and c
• E. b, c and e

Answer: (E)

Verified step by step guidance

1. Step 1: Understand the concept of electron affinity. Electron affinity is the energy change that occurs when an electron is added to a neutral atom. Generally, adding an electron to a non-metal is exothermic, meaning it releases energy.
2. Step 2: Analyze statement (a). Phosphorus has a less exothermic electron affinity compared to silicon and sulfur due to its half-filled p orbital, which is relatively stable.
3. Step 3: Examine statement (b). The second ionization energy of oxygen involves removing an electron from a positively charged ion, which requires more energy than removing an electron from a neutral fluorine atom. Therefore, this statement is false.
4. Step 4: Consider statement (c). As the principal quantum number increases, the effective nuclear charge experienced by the outer electrons generally decreases due to increased electron shielding, making this statement false.
5. Step 5: Evaluate statement (e). The second electron affinity is typically less exothermic (or even endothermic) than the first because adding an electron to a negatively charged ion requires more energy. Thus, this statement is false.