Question

determine whether k or rb that has the more negative (more exothermic) electron affinity.
rb
k
determine whether o or be that has the more negative (more exothermic) electron affinity.
o
be
determine whether si or p that has the more negative (more exothermic) electron affinity.
si
p
determine whether cl or al that has the more negative (more exothermic) electron affinity.
al
cl

Explanation:

• For K and Rb: Electron affinity generally becomes less negative (less exothermic) as we move down a group. Since K is above Rb in Group 1, K has a more negative electron affinity.
• For O and Be: O is in Group 16 and Be is in Group 2. O has a higher tendency to gain an electron (more negative electron affinity) as it needs two electrons to complete its octet, while Be has a filled \(2s\) sub - shell and is less likely to gain an electron.
• For Si and P: Si is in Group 14 and P is in Group 15. Si has a more negative electron affinity. In P, the addition of an electron would result in electron - electron repulsion in the half - filled \(3p\) sub - shell.
• For Cl and Al: Cl is in Group 17 and Al is in Group 13. Cl has a very high tendency to gain an electron (more negative electron affinity) as it needs only one electron to complete its octet, while Al has a relatively lower tendency to gain an electron.

Answer:

• K
• O
• Si
• Cl