Bromine (Br) is a chemical element with atomic number 35, and it is a member of the halogen group in the periodic table (Group 17). Like other halogens, bromine commonly forms ions with a specific charge based on its electron configuration and the tendency of halogens to gain electrons to achieve a stable noble gas configuration.
Charge of Bromine:
- Bromine typically forms a negative ion (anion) when it gains one electron to complete its outer electron shell. This results in the formation of the bromide ion (Br⁻).
- The charge on the bromide ion is -1. This is because bromine, in its neutral state, has 35 protons and 35 electrons, but when it gains one electron, it has 36 electrons and a net negative charge.
Reason for the Charge:
- Bromine has an electron configuration of [Ar] 3d¹⁰ 4s² 4p⁵. It is one electron short of a full outer electron shell (which would be a stable configuration like that of the noble gas krypton, with 36 electrons).
- To achieve this stable configuration, bromine tends to gain one electron in chemical reactions, resulting in the formation of the Br⁻ ion with a charge of -1. This is characteristic of all halogens (Group 17 elements), which typically form 1- anions.
Bromine in Compounds:
- When bromine reacts with metals or other elements to form compounds, it often bonds as a bromide (Br⁻) ion. For example, in sodium bromide (NaBr), sodium (Na) donates an electron to bromine, resulting in the formation of Na⁺ and Br⁻ ions.
- Bromine can also form other compounds where it may be in a positive oxidation state, such as in bromine dioxide (BrO₂) or bromine pentafluoride (BrF₅), but in these cases, bromine is typically still bonded with oxygen or fluorine and does not carry a simple charge like Br⁻.
Conclusion:
In most cases, bromine has a charge of -1 when it forms a bromide ion (Br⁻). This occurs because bromine gains one electron to complete its outer electron shell, achieving a stable configuration.