N.B. The first row elements have atomic numbers 3 to 10.

The graph follows a smooth decrease which reflects the increase in effective nuclear charge. The greater the effective nuclear charge the greater the force the positive nucleus will exert on the negative electrons and so the closer it will pull them and so the smaller the radius will be.

This trend is also observed in ionic and metallic radii across a period, and will increase down a group as more shells of electrons are added.

BACK TO MAIN PAGE