The atomic radius of lithium is typically found through experimental techniques like X-ray diffraction or by theoretical calculations. In practical terms, the accepted value is 134 picometers (pm), or 0.134 nanometers (nm).
Here's a breakdown of how the radius is determined and the different ways it can be expressed:
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Experimental Techniques:
- X-ray Diffraction: This method is used to determine the arrangement of atoms in a crystal. By analyzing the diffraction patterns, scientists can calculate the distances between atoms, which can then be used to estimate the atomic radius. This technique often gives the metallic radius when lithium is in its solid, metallic form.
- Other Spectroscopic Methods: Various spectroscopic techniques can also provide information about the electron distribution around the atom, which is related to the atomic size.
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Theoretical Calculations:
- Quantum Mechanical Calculations: Sophisticated computational methods based on quantum mechanics can be used to model the electronic structure of lithium and predict its atomic radius. These calculations take into account the interactions between the nucleus and the electrons.
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Units and Conversion:
- The atomic radius of lithium is commonly expressed in picometers (pm) or nanometers (nm).
- Conversion: 1 nm = 1000 pm
- Therefore, 134 pm = 0.134 nm
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Different Types of Radii:
- Atomic Radius (also called the covalent radius): This is half the distance between the nuclei of two identical atoms joined by a single covalent bond. For lithium, this is often the value cited.
- Metallic Radius: This is half the distance between the nuclei of two adjacent atoms in a solid metallic lattice.
- Ionic Radius: This is the radius of the lithium ion (Li+), which is smaller than the atomic radius because lithium loses an electron to form the ion.
In Summary: You generally find the radius by looking it up, as it's a measured or calculated value. For lithium, the atomic radius is accepted as 134 pm or 0.134 nm. This value is determined using experimental techniques such as X-ray diffraction or by theoretical calculations.
