The electron configuration of a barium ion with a charge of -1, written as Ba-1, is determined by removing one electron from the neutral barium atom (Ba).
The electron configuration of neutral barium (Ba) is: [Xe] 6s2.
To form the Ba-1 ion, we remove one electron from the 6s orbital. Therefore, the electron configuration of Ba-1 would be: [Xe] 6s1.
So, the correct electron configuration of the barium -1 ion (Ba-1) is [Xe] 6s1.