Answer
a) Xe < Sb < In.
b) Cl>Br>As
Work Step by Step
a. The electron configurations provided correspond to the elements in the periodic table. The electron configurations can be matched to the elements as follows:
1. \( [\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{6} \) corresponds to the element Xenon (Xe).
2. \( [\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{1} \) corresponds to the element Indium (In).
3. \( [\mathrm{Kr}] 5 s^{2} 4 d^{10} 5 p^{3} \) corresponds to the element Arsenic (As).
Across a period (left → right), atomic radius decreases because nuclear charge increases and electrons are added to the same principal shell.
So order of increasing size (small → large):
Xe < Sb < In.
b. The electron configurations provided correspond to the elements in the periodic table. The electron configurations can be matched to the elements as follows:
1. \( [\mathrm{Ne}] 3 s^{2} 3 p^{5} \) corresponds to the element Chlorine (Cl).
2. \( [\mathrm{Ar}] 4 s^{2} 3 d^{10} 4 p^{3} \) corresponds to the element Arsenic (As).
3. \( [\mathrm{Ar}] 4 s^{2} 3 d^{10} 4 p^{5} \) corresponds to the element Bromine (Br).
Ionization energy trend:
- Decreases down a group (atoms get larger).
- Increases across a period (atoms get smaller, nuclear attraction increases).
So order of decreasing first ionization energy (highest → lowest):
Cl>Br>As
