How many valence electrons are in a bromine atom?
The correct answer and explanation is:
Correct Answer: 7 valence electrons
Bromine is a chemical element with the symbol Br and atomic number 35. To determine the number of valence electrons in a bromine atom, examine its position on the periodic table. Bromine is located in Group 17, also known as the halogens. Elements in this group all have seven valence electrons in their outermost electron shell.
The electron configuration of a neutral bromine atom is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
From this configuration, the highest principal energy level is n = 4, which includes the 4s² and 4p⁵ orbitals. Adding the electrons in these orbitals gives a total of 7 electrons in the outer shell (2 from 4s and 5 from 4p). These are the valence electrons, which are the electrons available for bonding.
Valence electrons play a key role in determining an element’s chemical behavior. In the case of bromine, having seven valence electrons means it is one electron short of a full outer shell, which contains eight electrons (an octet). As a result, bromine is very reactive and tends to gain one electron during chemical reactions to achieve a stable electron configuration.
Bromine often forms a –1 anion (Br⁻) when it gains an electron. This tendency to accept an electron is typical of halogens. Its reactivity and valence electron configuration also explain bromine’s ability to form compounds such as hydrogen bromide (HBr) and sodium bromide (NaBr).
Understanding the number of valence electrons helps predict how elements interact, form compounds, and conduct electricity in chemical processes.