OK Chalk5,
Time for some basics.
1. The Nitrogen Rule: when the MW is EVEN (e.g.176) the N atom count is EVEN (N = 0, 2, 4, 6....) and vice versa.
When the MW is ODD (e.g. 177) the N atom count is ODD (N = 1, 3, 5...) and vice versa.
2. 176 is not an exact mass, it is NOMINAL. An EXACT mass might be measured as 176.0123; this would allow the determination of possible elemental compositions (C, H, N, O, S, Br, Cl, I, P, Si etc) consistent with 176.0123.
3. What are the characteristics of Br and Cl atoms that enable them to be confirmed or discounted in a mass spectrum ?
So now take two deep breaths, revisit your mass spectrum and call us in the morning.
Good Luck !!