How do the physical and chemical properties of the elemts change?

The physical and chemical properties of elements change in a systematic way across the Periodic Table, primarily due to variations in atomic structure, such as electron configuration and atomic size. As you move from left to right across a period, elements generally become less metallic and more non-metallic, with increasing electronegativity and ionization energy. Conversely, moving down a group, elements tend to exhibit increasing metallic character, larger atomic radii, and decreased ionization energy. These trends arise from the influence of nuclear charge and the shielding effect of inner electrons.