Reading trends in the periodic table
Colour the table by atomic radius, ionisation energy or electronegativity and hunt for periodic patterns.
Goal
State how atomic radius, first ionisation energy and electronegativity vary across a period and down a group, with exceptions.
Apparatus and reagents
Periodic-table widget with colour-coded properties and element slider.
Procedure
- Select the atomic-radius mode and scan period 2 from Li to Ne: how does the radius change?
- Switch to ionisation energy and repeat the scan; then compare Li→Ne with Na→Ar.
- Switch to electronegativity: find the most electronegative element and the least metallic region of the table.
- Use the element slider to compare a group — e.g. the alkali metals Li, Na, K — down the column.
What to observe
- Across a period the radius shrinks while ionisation energy and electronegativity grow (with small dips, e.g. N vs O).
- Down a group the radius grows and ionisation energy falls — metals become more reactive downward (alkali metals).
Explanation
Across a period the nuclear charge rises while electrons enter the same shell, so the shell is pulled inward and electrons are held more tightly. Down a group new shells are added: radius grows and the outermost electron is easier to remove. These trends — periodicity — are the deep content of Mendeleev’s table.
Chemists behind it
Virtual experiment: a simplified model to build intuition. It does not replace real lab work or safety training; never repeat chemistry at home without supervision.