Periodic trends (atomic radius, electronegativity, ionisation energy)

What it shows

Atomic properties change in regular patterns across the periodic table. Across a period, the nuclear charge increases while the number of electron shells stays the same, so atomic radius decreases while electronegativity and first ionisation energy increase. Down a group, each extra shell makes the atom larger and the outer electron easier to remove, so metallic character increases. Working with real data for the first 36 elements, students can also spot exceptions to the smooth trends, such as the small drops in ionisation energy from Be to B and from N to O.

How to use

Pick a Property, then set Chart by to Period or Group and choose which period or group to plot. Clicking an element cell shows its data and moves the chart to that element's period or group. Ask students to describe the trend from the chart before they read the conclusion underneath, then turn on Show values in cells to compare the numbers across the whole table.

Parameters you can change

• Property Atomic radius (pm), Electronegativity (Pauling), First ionisation energy (kJ/mol), Metallic / non-metallic character
• Chart by Period, Group
• Period (when viewing by period) 1–4
• Group (when viewing by group) IA, IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA
• Show values in cells

Questions to explore

1. Why does atomic radius decrease from Na to Cl across period 3?
2. Which of the first 36 elements has the highest electronegativity, and where is it in the periodic table?
3. Why does first ionisation energy generally increase across a period, and why is it lower for B than Be?