Arrangement of elements
Trends Across a Period (Left to Right)
As you move across a period:
- Metallic Character: Decreases. Elements become less metallic and more non-metallic.
- Oxide Nature: Changes from basic (metal oxides, e.g., Na_2O) to amphoteric (e.g., Al_2O_3) to acidic (non-metal oxides, e.g., SO_3).
- Atomic Radius: Decreases. The proton number increases, pulling the same number of shells closer to the nucleus.
Key Boundary: The transition from metal to non-metal happens around Group 14/15. Silicon (Group 14) is a metalloid.