Variation of metallic and nonmetallic properties in the periodic table:
Metallic properties
(Metals tend to lose electrons easily, form positive ions, and are good conductors.)
- Across a period (left → right): Metallic character decreases.
- Atoms get smaller, hold electrons more tightly, and it becomes harder to lose electrons.
- Example: Sodium (metal) → Magnesium (metal but less metallic) → Aluminum (weak metal) → Silicon (metalloid) → Phosphorus (nonmetal).
- Down a group (top → bottom): Metallic character increases.
- Atoms get larger, outer electrons are farther from the nucleus, and it becomes easier to lose them.
- Example: Lithium → Sodium → Potassium (increasing metallic strength).
Nonmetallic properties
(Nonmetals tend to gain or share electrons, form negative ions, and are poor conductors.)
- Across a period (left → right): Nonmetallic character increases.
- Atoms more strongly attract electrons as size decreases.
- Example: Carbon → Nitrogen → Oxygen → Fluorine (strongest nonmetal).
- Down a group (top → bottom): Nonmetallic character decreases.
- Larger atoms attract extra electrons less strongly.
- Example: Fluorine → Chlorine → Bromine → Iodine (nonmetallic property weakens).
In short:
- Across a period: Metallic ↓ , Nonmetallic ↑
- Down a group: Metallic ↑ , Nonmetallic ↓