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Chemistry - Periodic Variations (6 of 23) Atomic Radius: What Determines the Radius? 2nd Period By Michel van Biezen

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Chemistry - Periodic Variations (6 of 23) Atomic Radius: What Determines the Radius? 2nd Period By Michel van Biezen


Summary:


  1. Introduction to Second Period Elements:

    • Focus on the left side of the periodic table, starting with lithium, then beryllium, boron, carbon, nitrogen, oxygen, and fluorine.

  2. Atomic Structure Analysis:

    • Transitioning from helium to lithium, the third electron is added to the S orbital on the second energy level, leading to a large atom due to partial screening by inner electrons.
    • Beryllium, with an additional proton in the nucleus, has a stronger force of attraction on the two outer electrons, resulting in a smaller atomic size compared to lithium.
    • Similar trends continue with boron, carbon, nitrogen, oxygen, and fluorine, where increasing nuclear charge leads to smaller atomic sizes due to stronger attraction to outer electrons and consistent screening effect by inner electrons.

  3. Periodicity in Atomic Radii:

    • The trend shows that as nuclear charge increases from left to right across the second period, atomic sizes decrease accordingly.
    • The screening effect remains relatively constant for all elements in the second period, contributing to the observed trend in atomic radii.

  4. Comparison of Metallic and Covalent Radii:

    • Metallic radii measurements are used for elements on the left side, while covalent radii are more appropriate for representative elements on the right side.
    • Metallic radii are convenient for measuring the volume of metallic blocks, while covalent radii are determined based on bonding with other elements.

  5. Conclusion:

    • The observed periodicity in the second period demonstrates how atomic radii decrease due to increasing nuclear charge and consistent screening effect by inner electrons.
    • The trend illustrates the relationship between nuclear charge, electron arrangement, and atomic size across the second period.

This summary provides insights into how the atomic radii of second period elements vary based on their electron structure and nuclear charge, highlighting the periodic trend observed in the periodic table.