Final answer:
The atomic radius of a lithium atom is found in chemistry data tables and is 134 picometers, which is 0.134 nanometers. It is determined indirectly by methods such as x-ray diffraction.
Step-by-step explanation:
To calculate the atomic radius of a lithium atom, we utilize the atomic radius value that is typically found in data tables in chemistry. For lithium, this value is 134 picometers (pm) across. To convert this value to nanometers (nm), we use the conversion factor where 1 nm is equivalent to 1000 pm. Therefore, the atomic radius of a lithium atom is 134 pm / 1000 = 0.134 nm.
The methodology to determine atomic radius without direct measurement involves techniques such as x-ray diffraction, which allows us to calculate molecular and atomic sizes by observing how x-rays are diffracted through a crystal lattice of the compound. This is possible due to the fact that x-rays have wavelengths on the same scale as the distances between atoms in a crystal lattice.
When dealing with ions, such as a lithium ion, which is smaller than its neutral atom counterpart due to loss of an electron, the atomic radius of an ion (ionic radius) may also be calculated. Using crystallography data, the ionic radius can be obtained by analyzing the edge length of the unit cell within the crystal structure. For instance, it has been found that the lithium ion has a radius of 90 pm.
The atomic radius describes the size of an atom and is measured in picometers. Advancements in techniques like x-ray crystallography have enabled scientists to measure atomic radii with high precision, despite the inability to measure such small distances directly with conventional tools.
Changes in atomic radius throughout the periodic table occur due to trends in electron configuration and effective nuclear charge, with atomic radius generally increasing from top to bottom within a group and decreasing across a period from left to right.