Why do atomic radii increase going down a group of the periodic table?

Verified step by step guidance

Step 1: Understand that atomic radius is the distance from the nucleus of an atom to the outermost electron shell.

Step 2: Recognize that as you move down a group in the periodic table, each element has an additional electron shell compared to the one above it.

Step 3: Note that with each additional electron shell, the outermost electrons are further from the nucleus, increasing the atomic radius.

Step 4: Consider the effect of electron shielding, where inner electron shells partially block the attraction between the nucleus and the outermost electrons, allowing the atomic radius to increase.

Step 5: Conclude that the combination of additional electron shells and increased electron shielding results in a larger atomic radius as you move down a group.

Key Concepts

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

Atomic Radius

The atomic radius is defined as the distance from the nucleus of an atom to the outermost shell of electrons. It is a measure of the size of an atom and can vary depending on the atom's environment and bonding. Understanding atomic radius is crucial for analyzing trends in the periodic table.

Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements as one moves across or down the periodic table. These trends include atomic radius, ionization energy, and electronegativity. Recognizing these trends helps explain why atomic radii increase down a group due to the addition of electron shells.

Electron Shielding

Electron shielding occurs when inner-shell electrons repel outer-shell electrons, reducing the effective nuclear charge felt by the outer electrons. As you move down a group, additional electron shells are added, increasing shielding and allowing outer electrons to be further from the nucleus, which contributes to the increase in atomic radius.

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