group 1, 2, 3 are metals..
grp 5, 6, 7 consist of some metals and non-metals. but for O level
syllabus, only teach the non-metals..
when metals lose electrons, they become positively charged, since
the charge of electrons is -1
and hence when non-metals gains 1 electron, they become negatively
charge..
as for the no. of electrons in the shell, it can be calculated by
the simple formula, 2n^2, where 'n' is the shell number
but for the 3rd shell, it can only have 8 electrons, instead of
2(3^2) = 18..reason, i've forgotten
