Non-Metallic Character: Periodic Trends You Must Know
What Is Non-Metallic Character?
Non-metallic character describes how easily an atom gains electrons to form negative ions. In simpler terms, nonmetals prefer to attract electrons during chemical bonding.
For example:
- Fluorine (F) gains 1 electron:
F(g) + 1e⁻ → F⁻(g) - Oxygen (O) gains 2 electrons:
O(g) + 2e⁻ → O²⁻(g) - Therefore, elements with high electron affinity and high electronegativity behave more like nonmetals.
What Factors affects Periodic Trend For Non-Metallic Character?
Non-metallic character depends on two major factors:
1. Atomic Size
Smaller atoms pull electrons closer because the nucleus lies nearer to the valence shell. Thus, small atoms attract electrons more strongly.
2. Ionization Energy
Atoms with high ionization energy hold onto their own electrons tightly. As a result, they also tend to attract additional electrons, increasing non-metallic behavior.
How Does Non-Metallic Character Change in the Periodic Table?
Across a Period (Left to Right): Non-Metallic Character Increases
As you move across a period:
The number of protons increases
The effective nuclear charge strengthens
Atomic size decreases
Electron affinity increases
The tendency to gain electrons becomes stronger
Therefore, non-metallic character increases from left to right.
Example:
Elements like fluorine (F), oxygen (O), chlorine (Cl), and nitrogen (N) lie on the extreme right of the periodic table (excluding noble gases). These elements are highly non-metallic.
Down a Group (Top to Bottom): Non-Metallic Character Decreases
As you move down a group:
Atomic size increases
Valence electrons move farther from the nucleus
Shielding effect increases
Electron affinity decreases
The tendency to gain electrons becomes weaker
As a result, non-metallic character decreases down the group.
Example:
Elements like cesium (Cs), barium (Ba), rubidium (Rb), and strontium (Sr) lie at the bottom-left of the table and show the lowest non-metallic character.
Quick Summary of the Non-Metallic Character Periodic Trends
Across a Period:
➤ Non-metallic character increases as atomic size decreases and Z_eff increases
Down a Group:
➤ Non-metallic character decreases as atomic size increases and shielding increases
Takeaway points Non-Metallic Character Periodic Trends-
To identify nonmetals, look for:
High electron affinity
High electronegativity
Small atomic radius
The strongest nonmetals lie in the top-right corner of the periodic table, while the least nonmetals appear toward the bottom-left.