why does the change for the atomic radii of the elements in period 3 look similar to period 2?
The periodic table organizes elements based on their atomic structure and properties. Periods are horizontal rows in the periodic table, and each period corresponds to a new electron shell being filled. When we analyze the changes in atomic radii across different periods, we observe certain patterns.
In period 2, the atomic radii generally decrease from left to right. This trend can be attributed to the increasing nuclear charge as we move from left to right across the period. The additional protons in the nucleus attract the electrons more strongly, causing the electron cloud to shrink and the atomic radius to decrease.
Now, when we examine period 3, we can observe a similar trend - the atomic radii also generally decrease from left to right. This similarity is because, like period 2, as we move from left to right across period 3, the nuclear charge increases due to the additional protons in the nucleus.
However, there is an interesting exception in period 3, between sodium and magnesium. Despite the increased nuclear charge from sodium to magnesium, their atomic radii slightly increase. This anomaly can be explained by the electron configuration. In sodium, the additional electron enters a new electron shell, further from the nucleus, resulting in a larger atomic radius. In magnesium, the added electron enters the same electron shell, but experiences increased electron-electron repulsion, causing the atomic radius to decrease.
To summarize, the similarity in the trend of atomic radii between period 2 and period 3 arises from the increasing nuclear charge as we move from left to right across these periods. However, there may be exceptions depending on the electron configuration and electron-electron repulsion within a given period.