For elements in groups one to seven, the last number in the electron arrangement is the same as what? worth 20 points, answer.

As you go across each period from left to right the outer shell gradually becomes filled with electrons. the outer shell contains just one electron on the left hand side of the table, but is filled by the time you get to the right hand side.moving  down each group, you can see that  the number of electrons in the outermost shell is the same as the group number number.each element in a group therefore has the same number of electrons in its outer shell.i hope it you!

; lc

13) a 14) a15) b16) i don't know sorry17) a (maybe)