Which element will have the largest atomic radius?
potassium (K)
germanium (Ge)
calcium (Ca)
gallium (Ga)
Answer (1)
Identify the positions of K, Ca, Ga, and Ge on the periodic table.
Recall that atomic radius increases down a group and decreases across a period.
Since all elements are in the same period, compare their group positions.
Potassium (K) is furthest to the left, thus has the largest atomic radius: K .
Explanation
Problem Analysis We are asked to find the element with the largest atomic radius among Potassium (K), Germanium (Ge), Calcium (Ca), and Gallium (Ga) using their positions on the periodic table.
Locating Elements on Periodic Table First, let's locate each element on the periodic table:
Potassium (K) is in Group 1 (alkali metals) and Period 4.
Calcium (Ca) is in Group 2 (alkaline earth metals) and Period 4.
Gallium (Ga) is in Group 13 and Period 4.
Germanium (Ge) is in Group 14 and Period 4.
Trends in Atomic Radius Atomic radius generally increases as you move down a group (column) and decreases as you move from left to right across a period (row).
Comparing Element Positions All four elements are in the same period (Period 4). Therefore, we only need to consider their group positions. Moving from left to right, the order is K, Ca, Ga, Ge. Since atomic radius decreases from left to right across a period, the element furthest to the left will have the largest atomic radius.
Determining Largest Atomic Radius Potassium (K) is the furthest to the left in Period 4 among the given elements. Therefore, Potassium (K) has the largest atomic radius.
Examples
Understanding atomic radius trends helps in predicting chemical reactivity. For example, elements with larger atomic radii tend to lose electrons more easily, making them stronger reducing agents. This knowledge is crucial in designing batteries, understanding corrosion, and developing new materials with specific properties. Imagine designing a solar cell; knowing which elements readily donate electrons can help you create a more efficient energy conversion system.
