where do you find the atoms with the largest atomic radius on the periodic table
Where do you find the atoms with the largest atomic radius on the periodic table?
Answer:
Atoms with the largest atomic radius are typically found at the bottom left of the periodic table. This trend occurs due to two primary factors: the increasing principal quantum number (n) and the effective nuclear charge (Z_{\text{eff}}).
Solution By Steps:
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Understanding Atomic Radius Trends:
- Vertical Trend (Groups): As you move down a group (column) in the periodic table, the atomic radius increases. This is because each successive element has an additional electron shell (higher principal quantum number (n)), which increases the distance between the outermost electrons and the nucleus, thereby increasing the atomic radius.
- Horizontal Trend (Periods): As you move across a period (row) from left to right, the atomic radius decreases. This is due to the increase in the effective nuclear charge (Z_{\text{eff}}). With each additional proton in the nucleus, the positive charge increases, pulling the electron cloud closer to the nucleus and reducing the atomic radius.
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Combining the Trends:
- The largest atomic radii are found in the elements at the bottom of a group, as these elements have the most electron shells.
- Among these elements, those on the left of the periodic table have fewer protons and a lower effective nuclear charge compared to those on the right in the same period, resulting in a larger atomic radius.
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Specific Example:
- Cesium (Cs) and Francium (Fr) are examples of elements with very large atomic radii. Both are located in Group 1 (the alkali metals) at the bottom of the periodic table. Francium (Fr) has the largest atomic radius of all naturally occurring elements.
\text{Francium (Fr)} = [Rn] 7s^1-
Another example is Rubidium (Rb), which is directly above Cesium in Group 1 and also has a large atomic radius, though slightly smaller than Cesium’s and Francium’s.
\text{Rubidium (Rb)} = [Kr] 5s^1
In summary, the atoms with the largest atomic radius can be found at the bottom left of the periodic table, specifically among the alkali metals in Group 1. The trend of increasing atomic radius moving down a group and the decrease in effective nuclear charge moving left across a period explains why elements like Francium have the largest atomic radii.