Based on their positions in the periodic table, predict which atom of the following pairs will have the smaller first ionization energy: (a) $\mathrm{Br}, \mathrm{Kr} ; \mathbf{( b )} \mathrm{C}, \mathrm{Ca} ;(\mathbf{c}) \mathrm{Li}, \mathrm{Rb} ;\(; (d) \)\mathrm{Pb}, \mathrm{Si} ;$ (e) \(\mathrm{Al}, \mathrm{B}\).

Short Answer

Expert verified
The elements with smaller first ionization energies in each pair are: (a) Br, (b) Ca, (c) Rb, (d) Pb, and (e) Al.

Step by step solution

01

(a) Comparing Br and Kr

Br (Bromine) is in Group 17 (7A) and Period 4, while Kr (Krypton) is in Group 18 (8A) and also Period 4. Since they are in the same period and ionization energy generally increases from left to right within a period, Br will have the smaller first ionization energy compared to Kr.
02

(b) Comparing C and Ca

C (Carbon) is in Group 14 (4A) and Period 2, while Ca (Calcium) is in Group 2 (2A) and Period 4. The ionization energy decreases from top to bottom within a group, so Ca (being lower in the periodic table) will have the smaller first ionization energy compared to C.
03

(c) Comparing Li and Rb

Li (Lithium) is in Group 1 (1A) and Period 2, while Rb (Rubidium) is in Group 1 (1A) and Period 5. Since they are in the same group, we will apply the trend that ionization energy decreases from top to bottom and determine that Rb will have the smaller first ionization energy compared to Li.
04

(d) Comparing Pb and Si

Pb (Lead) is in Group 14 (4A) and Period 6, while Si (Silicon) is in Group 14 (4A) and Period 3. As they are in the same group, ionization energy decreases from top to bottom within a group, so Pb will have the smaller first ionization energy compared to Si.
05

(e) Comparing Al and B

Al (Aluminum) is in Group 13 (3A) and Period 3, while B (Boron) is in Group 13 (3A) and Period 2. Since they are in the same group, we will apply the trend that ionization energy decreases from top to bottom within a group, thereby concluding that Al will have the smaller first ionization energy compared to B.

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