## Chemistry and Chemical Reactivity (9th Edition)

a) 158 peak: $^{79}Br_2$; 160 peak: $^{79}Br^{81}Br$; 162 peak: $^{81}Br_2$; b) Since both isotopes have a relative abundance of roughly 50%, the peaks are proportional to the number of possible combinations between them. The 160 peak has two possible combinations ($^{79}Br^{81}Br$ and $^{81}Br^{79}Br$) vs one for each of the other two, which explains the ratio of intensities of the peaks (1:2:1).