Determining the atomic size (atomic radius) of sodium involves understanding its position on the periodic table and the trends in atomic size. Here's how you can find it:
Understanding Atomic Radius Trends
Atomic radius generally increases as you move down a group (vertical column) in the periodic table and decreases as you move from left to right across a period (horizontal row).
- Down a Group: As you go down a group, more electron shells are added, causing the outer electrons to be farther from the nucleus.
- Across a Period: As you go across a period, the number of protons in the nucleus increases, which increases the effective nuclear charge. This pulls the electrons closer to the nucleus, reducing the atomic radius.
Locating Sodium on the Periodic Table
Sodium (Na) is in Group 1 (alkali metals) and Period 3 of the periodic table.
Comparing Sodium to Neighboring Elements
Based on periodic trends:
- Sodium is larger than magnesium (Mg), which is to its right in Period 3. The video excerpt confirms this: "Let's look at which of these atoms is larger we have mg and na that's magnesium. And sodium." The increasing nuclear charge from left to right pulls the electrons in magnesium closer to the nucleus compared to sodium.
- Sodium is smaller than potassium (K), which is below it in Group 1. Potassium has an additional electron shell.
Experimental Methods for Determining Atomic Radius
While periodic trends provide a good estimate, the atomic radius is often determined experimentally using techniques such as:
- X-ray diffraction: This technique is used to measure the distances between atoms in a solid. For metallic sodium, this can give you an estimate of the atomic radius.
- Quantum mechanical calculations: Sophisticated computer models can also estimate atomic radii.
Reported Atomic Radius
The atomic radius of sodium is generally reported to be around 186 picometers (pm) or 1.86 Angstroms. Keep in mind that there are different ways to define "atomic radius" (e.g., metallic radius, covalent radius), so the exact value may vary slightly depending on the source and method used.
