Trends across the periodic table: an interactive table of the main-group elements, periods 1 to 6, that recolours by atomic radius, first ionisation energy, electronegativity, state at room temperature or reactivity with water, where you can step through the elements in order of atomic number and see a bar chart of the trend across a period or down a group.
Add protons and atoms get smaller
Step across a period and every element has one more proton and one more electron than the last, yet the atom shrinks. Step down a group and it swells again. Those two gradients run under every trend across the periodic table. Pick a property to recolour the table, then step through the elements and watch the radius shrink across each period.
Periodic table trendsRadius · Na
Pick a property, then step through the elements and watch the trend
Across period 3 · radius shrinks
ElementZ = 11 · sodium
H · Z 1atomic number →Rn · Z 86
Na · atomic radius
166 pm
Na · electron shells
2,8,1
1s² 2s² 2p⁶ 3s¹
Know This
Across a period rising core charge pulls the outer shell in, down a group each extra electron shell pushes it out, and that distance decides how tightly an atom holds its outer electrons.