Expert Verified • Chemistry
Periodic Table Trends
How properties of elements change across the table.
The **Periodic Table Trends** are patterns observed in the properties of elements as you move across a period (left to right) or down a group (top to bottom) in the periodic table. These trends include **atomic radius**, **ionization energy**, **electronegativity**, and **metallic character**. Understanding these trends is crucial because they help predict how elements behave chemically and physically. For example, elements with low ionization energy tend to lose electrons easily, making them good conductors of electricity. Key trends include: 1. **Atomic Radius** decreases across a period due to increased nuclear charge but increases down a group due to additional electron shells. 2. **Ionization Energy** generally increases across a period and decreases down a group. 3. **Electronegativity** increases across a period and decreases down a group. 4. **Metallic Character** decreases across a period and increases down a group. These trends are essential for students as they form the foundation for understanding chemical reactions, bonding, and material properties.
Quick Recall Points
1
Atomic radius decreases across a period and increases down a group.2
Ionization energy increases across a period and decreases down a group.3
Electronegativity increases across a period and decreases down a group.4
Metallic character decreases across a period and increases down a group.5
Understanding trends helps predict chemical behavior and reactivity.Active Recall Challenge
Test your understanding before you leave.
What happens to atomic radius as you move from left to right across a period?
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Why does atomic radius decrease across a period?
Atomic radius decreases across a period because the nuclear charge increases, pulling electrons closer to the nucleus despite the addition of electrons in the same shell.
Why does ionization energy decrease down a group?
Ionization energy decreases down a group because the atomic radius increases, causing the outermost electrons to be farther from the nucleus and thus easier to remove.
What is the relationship between electronegativity and metallic character?
Electronegativity and metallic character are inversely related. As electronegativity increases across a period, metallic character decreases, and vice versa down a group.
Why are noble gases excluded from trends in ionization energy?
Noble gases have a full valence shell, making them extremely stable and resistant to losing electrons, so their ionization energies are exceptionally high and do not follow the general trend.