What is the predicted order of first ionization energies from highest to lowest for lithium (Li), sodium (Na), potassium $( K )$, and rubidium $( Rb )$?
A. $Rb > K > Na > Li$
B. $K > Rb > Na > Li$
C. $Li > Na > K > Rb$
D. $Rb > K > Li > Na$
Answer (1)
Identify the elements: Lithium (Li), Sodium (Na), Potassium (K), and Rubidium (Rb) are Group 1 elements.
Recall the ionization energy trend: Ionization energy decreases down a group.
Arrange the elements: Li > Na > K > Rb.
State the predicted order: Na > K > Rb}"> L i > N a > K > R b
Explanation
Understanding the Problem We are asked to predict the order of first ionization energies for the elements lithium (Li), sodium (Na), potassium (K), and rubidium (Rb). Ionization energy generally decreases as you go down a group in the periodic table.
Ionization Energy Trend Lithium (Li), sodium (Na), potassium (K), and rubidium (Rb) are all in Group 1 (alkali metals) of the periodic table. As you move down a group, the atomic size increases, and the outermost electrons are further from the nucleus. This increased distance and the shielding effect of inner electrons make it easier to remove an electron, resulting in a lower ionization energy.
Determining the Order Based on their positions in Group 1, the order from top to bottom is: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb). Therefore, the ionization energy decreases in the same order: Na > K > Rb"> L i > N a > K > R b .
Examples
Understanding ionization energy is crucial in various fields, such as chemistry and material science. For example, predicting the reactivity of alkali metals in chemical reactions relies on knowing their ionization energies. Lithium, with the highest ionization energy among the group, requires more energy to lose an electron compared to rubidium, which has the lowest ionization energy. This difference in ionization energies explains why rubidium reacts more vigorously with water than lithium.
