Periodic trends
Pick a property to color the table. Darker tiles have higher values.
Atoms shrink across a period and grow down a group
Each ball is drawn to scale from the element's atomic radius.
Across period 2: lithium to fluorine
More protons pull the same shell in tighter.
The pattern repeats every period
Plot a property against atomic number and the same shape comes back each row. That repeat is why it's called a periodic table. Noble gases (orange) sit at the peaks of ionization energy; alkali metals (blue) sit in the valleys.
Elements 1–88. Atomic number along the bottom.
Trend summary
| Property | Left to right | Top to bottom | Why |
|---|---|---|---|
| Atomic radius | Decreases | Increases | More protons pull harder across; new shells add size down. |
| Electronegativity | Increases | Decreases | Small atoms with strong nuclear pull attract bonding electrons more. |
| Ionization energy | Increases | Decreases | Electrons held closer and tighter take more energy to remove. |
| Electron affinity | Generally increases | Generally decreases | Atoms close to a full shell release energy when they gain an electron. |
| Metallic character | Decreases | Increases | Metals lose electrons easily, which is easiest bottom-left. |
Periodic trend questions
What are the periodic trends?
Repeating patterns in element properties. Across a period (left to right), atomic radius shrinks while electronegativity and ionization energy rise. Down a group, atomic radius grows while electronegativity and ionization energy fall.
Why does atomic radius decrease across a period?
Each step right adds a proton, so the nucleus pulls harder, but the new electron goes into the same shell. The stronger pull draws that shell in.
Why does atomic radius increase down a group?
Each step down adds a whole new electron shell, farther from the nucleus. Inner electrons also shield the outer ones from the nucleus's pull.
Which element has the highest electronegativity?
Fluorine, at 3.98 on the Pauling scale. The least electronegative are cesium and francium, at about 0.7 to 0.8.
Which element has the highest ionization energy?
Helium (24.6 eV). Its two electrons sit close to the nucleus in a full shell, so removing one takes the most energy of any element.