Which periodic group has the SMALLEST atomic radius? Alkali Metals Halogens Noble Gases Transition Metals
The Correct Answer and Explanation is:
The group with the smallest atomic radius among the options is Noble Gases.
Explanation:
Atomic radius refers to the size of an atom, typically measured from the nucleus to the outermost electron shell. Several factors influence atomic radius, including the number of electron shells and the effective nuclear charge (the net positive charge experienced by the valence electrons).
Noble Gases:
- The noble gases, which belong to Group 18 of the periodic table, have the smallest atomic radii because they are chemically stable due to their full outer electron shells. This stability results in a very tight hold on their electrons, reducing the atomic radius.
- Additionally, noble gases have a high effective nuclear charge, as their protons outnumber the shielding effect of the inner electrons. This pulls the electron cloud inward, minimizing the atomic size.
Alkali Metals (Group 1):
- Alkali metals (like lithium, sodium, potassium) have the largest atomic radii within their respective periods. These elements have only one valence electron, and their effective nuclear charge is relatively low compared to other elements, meaning their electron clouds are spread out.
- As you move down the group, the atomic radius increases due to the addition of electron shells, despite the increasing nuclear charge, because the outer electrons are farther from the nucleus.
Halogens (Group 17):
- Halogens (like fluorine, chlorine, bromine) have smaller atomic radii than alkali metals, but they are still larger than those of noble gases. Halogens have one electron less than noble gases, resulting in a smaller effective nuclear charge but still a relatively compact size due to their high electronegativity.
Transition Metals:
- Transition metals (like iron, copper, zinc) have intermediate atomic radii compared to alkali metals, halogens, and noble gases. These elements possess multiple electron shells, but the presence of d-electrons complicates the atomic radius trend, as these electrons experience less shielding.
Thus, Noble Gases have the smallest atomic radius due to their stable, full electron shells and high effective nuclear charge.
