Wiktionary
n. (context chemistry English) In the periodic table of the elements, any of the eight groups (columns) of element that contain the lightest (and most common) elements.
Usage examples of "main group".
Saryn's supposed to get the ones headed for the stable, and then rejoin the main group.
Reave went back to meet them, but before he could reach the main group, Showcross Gee detached himself from the other twenty-six and headed him off.
And after the battles, Ender and Bean and four other soldiers would leave the main group and practice strange maneuvers.
The main group of security people was a hundred yards from Boeing and as I neared it a big man with a two-way radio slung at toe shoulder came forward to meet me.
It was magnificently executed, and the central figure of the main group reminded me sharply of my little friend Xhai.