| Member | Definition | Role |
|---|
| aluminum | | aluminium atom; aluminium(0) |
| boron | | boron atom |
| gallium | A metallic element predicted as eka-aluminium by Mendeleev in 1870 and discovered by Paul-Emile Lecoq de Boisbaudran in 1875. Named in honour of France (Latin Gallia) and perhaps also from the Latin gallus cock, a translation of Lecoq. | gallium atom |
| indium | A metallic element first identified and named from the brilliant indigo (Latin indicum) blue line in its flame spectrum. | indium atom |
| thallium | A metallic element first identified and named from the brilliant green line in its flame spectrum (from Greek thetaalphalambdalambdaomicronsigma, a green shoot). | thallium |