Answer
a. \( \mathrm{Ba} \)
b. \( \mathrm{K} \)
c. \( \mathrm{N} \)
d. \( \mathrm{S}^{2-} \)
e. \( \mathrm{Cs} \)
Work Step by Step
The ionization energy is the energy required to remove an electron from an atom or ion.
It generally increases as you move from left to right across a period and decreases as you move down a group on the periodic table. Therefore, in each set, the atom or ion with the smallest ionization energy is the one located at the bottom right of the group or period.
a. Ca, Sr, Ba
Group 2 alkaline earth metals → ionization energy decreases down the group.
Ba is the largest atom → lowest ionization energy.
Answer: \( \mathrm{Ba} \)
b. K, Mn, Ga
K: group 1, period 4 → very low IE
Mn: transition metal, period 4 → moderate IE
Ga: group 13, period 4 → higher IE
Answer: \( \mathrm{K} \)
c. N, O, F
Same period → ionization energy increases across the period (left → right)
Answer: \( \mathrm{N} \)
d. S²⁻, S, S²⁺
Anions have lower IE; cations have higher IE
Answer: \( \mathrm{S}^{2-} \)
e. Cs, Ge, Ar
Cs: group 1, period 6 → very low IE
Ge: group 14, period 4 → higher IE
Ar: noble gas → very high IE
Answer: \( \mathrm{Cs} \)
