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Ch.5 - Periodicity & Electronic Structure of Atoms
Chapter 5, Problem 121

Order the following atoms according to increasing atomic radius: Rb, Cl, As, K.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Radius

Atomic radius is a measure of the size of an atom, typically defined as the distance from the nucleus to the outermost electron shell. It varies across the periodic table, generally increasing down a group due to the addition of electron shells and decreasing across a period due to increased nuclear charge, which pulls electrons closer to the nucleus.
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Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across or down the periodic table. For atomic radius, the trend shows that elements in the same group have larger radii as you go down, while elements in the same period have smaller radii as you move from left to right due to effective nuclear charge.
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Group and Period Positioning

The position of an element in the periodic table, defined by its group (vertical column) and period (horizontal row), significantly influences its atomic radius. For instance, rubidium (Rb) and potassium (K) are in Group 1 and have larger atomic radii compared to chlorine (Cl) and arsenic (As), which are in Groups 17 and 15, respectively, leading to a clear ordering based on their positions.
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