Periodic Properties - Metallic and Non-metallic Characters

Metallic Character: The tendency of an atom to lose electrons and form cations (positively charged ions).

Nonmetallic Character: The tendency of an atom to gain electrons and form anions (negatively charged ions).

Periodic Trends:

1. Down a Group

• Metallic character increases as atomic size increases, reducing the effective nuclear charge on valence electrons, making them easier to lose.
• Nonmetallic character decreases since the attraction for additional electrons weakens.

2. Across a Period (Left to Right)

• Metallic character decreases as nuclear charge increases, pulling valence electrons closer and making them harder to lose.
• Nonmetallic character increases as electronegativity rises, making elements more likely to gain electrons.

Electropositivity (Metallic Nature): The ability to lose electrons (increases down a group, decreases across a period).

Electronegativity (Nonmetallic Nature): The ability to gain electrons (decreases down a group, increases across a period).

Reactivity of Elements:

• Highly electropositive metals (e.g., alkali metals) react easily by losing electrons.
• Highly electronegative nonmetals (e.g., halogens) react by gaining electrons.

The zig-zag line in the periodic table separates metals (left), nonmetals (right), and metalloids (borderline elements), explaining the transition in their chemical properties.