Final answer:
Bromine (Br), located in Group 17 (halogens) of the periodic table, is most likely to form a negative ion, as halogens tend to gain electrons forming anions.
Step-by-step explanation:
Based on its location on the periodic table, Bromine (Br) would be most likely to form a negative ion. This is because Bromine is located in Group 17 (the halogens), which are known for their high electron affinity and tendency to gain an electron to achieve a full valence shell, thus forming an anion (negatively charged ion). Elements from this group typically form anions with a charge of 1-, such as Br−.