All matter is composed of atoms containing protons, neutrons, and electrons. Protons and neutrons reside within the nucleus, while electrons orbit in specific energy shells. In a neutral atom, the number of positively charged protons is balanced by the number of negatively charged electrons. When an atom gains or loses electrons, it forms an electrically charged particle known as an ion. This article determines the precise number of electrons in the bromide ion, represented by the chemical symbol \(\text{Br}^-\).
Finding the Electron Count for Neutral Bromine
The electron count for any atom starts with identifying its atomic number (Z), which represents the count of protons found in the nucleus. This number is unique to each element and dictates its chemical identity. Bromine (\(\text{Br}\)) possesses an atomic number of 35.
This atomic number signifies that a bromine atom contains 35 protons. In a neutral atom, the total electrical charge must equal zero, meaning the number of negatively charged electrons must be identical to the number of positively charged protons. Therefore, a neutral bromine atom contains 35 electrons, which serves as the fundamental baseline count for calculations.
Interpreting the Negative Charge
Atoms often undergo chemical transformations to achieve a stable configuration, which frequently involves becoming an ion. An ion is an atom or molecule that carries a net electrical charge due to an imbalance between protons and electrons. The notation \(\text{Br}^-\) indicates that the bromine atom is no longer electrically neutral and has acquired a charge of negative one.
A negative charge on an ion means that the atom has acquired one or more extra electrons beyond its neutral count. An ion with a net negative charge is called an anion, formed when an atom gains electrons. The single minus sign in the \(\text{Br}^-\) symbol precisely denotes the gain of one electron.
To determine the final electron count, one must simply add one electron to the established count for the neutral bromine atom. This rule of adjusting the electron count based on the magnitude of the negative charge is universally applied to all anions.
Calculating the Total Electrons in \(\text{Br}^-\)
The final step in determining the electron count for the bromide ion involves combining the baseline count with the charge adjustment. The calculation begins with the confirmed number of electrons in the neutral bromine atom, which is 35. The negative charge on the \(\text{Br}^-\) ion indicates that the atom gained one additional electron during the process of ion formation.
By adding the gained electron to the initial neutral count, the total number of electrons in the bromide ion is calculated as \(35 + 1\), equaling 36 electrons. This resulting number of 36 electrons is the final answer for the specific particle \(\text{Br}^-\). This configuration is chemically significant because the bromide ion now possesses the same number of electrons as the nearest noble gas, Krypton (\(\text{Kr}\)).