What are some common mistakes students make with periodic trends?

The periodic trend of atomic size is one of the most frequent errors committed by students.

The atoms actually shrink as a period progresses. You might assume that when protons, electrons, and neutrons are added, the atoms would grow larger. However, this is not the case because an increase in protons (a higher effective nuclear charge) exerts even more force on the negatively charged electrons surrounding the nucleus. As a result, as a period progresses, the atoms shrink from left to right within the same period.

Some common mistakes students make with periodic trends include:

1. Confusing atomic size and atomic radius.
2. Misinterpreting the periodic trend for ionization energy or electronegativity.
3. Failing to account for exceptions to periodic trends, such as the noble gas configuration or transition metal anomalies.
4. Overgeneralizing trends across periods or groups without considering specific elements and their electronic configurations.
5. Forgetting the effect of nuclear charge, shielding, and electron-electron repulsion on periodic trends.
6. Not considering the influence of external factors, such as molecular structure or intermolecular forces, on observed trends.
7. Relying solely on memorization rather than understanding the underlying principles driving periodic trends.