An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?
Answer (2)
Identify that Mg, Ca, and Sr are in Group 2 and form +2 ions.
Recall that ionic radius increases down a group.
Determine the order of elements in Group 2: Mg, Ca, Sr.
Conclude that Sr forms the ion with the largest ionic radius: S r
Explanation
Understanding the Problem We are given a periodic table excerpt and asked to determine which of the listed elements (Mg, Sr, Ca) will form the ion with the largest ionic radius.
Analyzing the Elements The elements are Mg, Sr, and Ca. We need to consider the typical ions formed by these elements and their positions on the periodic table. Mg, Sr, and Ca are all in Group 2 (alkaline earth metals) and tend to form +2 ions. Ionic radius increases down a group in the periodic table.
Stating the Objective The objective is to determine which of the elements Mg, Sr, and Ca will form the ion with the largest ionic radius.
Planning the Solution The solution plan is to determine the typical ion formed by each element, locate the elements on the periodic table and identify their group, recognize that ionic radius increases down a group, compare the positions of Mg, Sr, and Ca within Group 2, and the element furthest down the group will form the ion with the largest ionic radius.
Determining the Largest Ionic Radius Mg, Sr, and Ca are all in Group 2 (alkaline earth metals) and form +2 ions (Mg 2 + , Sr 2 + , Ca 2 + ). As we move down Group 2, the ionic radius increases. The order of these elements in Group 2 is Mg, Ca, Sr. Therefore, Sr is furthest down the group, and Sr 2 + will have the largest ionic radius.
Final Answer Therefore, Sr will form the ion with the largest ionic radius.
Examples
Understanding ionic radius trends is crucial in various fields, such as materials science and geochemistry. For instance, when designing new ceramic materials, the size and charge of the constituent ions influence the crystal structure and properties of the material. Similarly, in geochemistry, the ionic radius of elements affects their distribution in minerals and their behavior during geological processes. Knowing that ionic radius increases down a group helps predict how different elements will interact in these systems.
The device delivers a current of 15.0 A for 30 seconds, which results in a total charge of 450 coulombs. This amounts to approximately 2.81 x 10^{21} electrons flowing through the device. Thus, about 2.81 trillion trillion electrons pass through it during this time.
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