Atoms consist of a central nucleus, which contains positively charged particles called protons and neutral particles called neutrons. Orbiting this nucleus are negatively charged particles known as electrons. The balance between these charged particles determines an atom’s overall electrical state.
Under certain conditions, atoms can gain or lose electrons, altering their charge balance. When this occurs, the atom transforms into an ion, which is a particle with a net electrical charge.
The Bromine Atom: A Starting Point
To determine the number of electrons in a bromide ion, it is helpful to first understand the neutral bromine atom. Every element is defined by its atomic number, which represents the precise number of protons in the nucleus of each atom of that element. For bromine, the atomic number is 35. This means that every bromine atom inherently contains 35 protons.
In a neutral atom, the number of electrons orbiting the nucleus is exactly equal to the number of protons. This equality ensures that the positive charges from the protons are balanced by the negative charges from the electrons, resulting in an atom with no net electrical charge. Therefore, a neutral bromine atom possesses 35 electrons.
The Bromide Ion: A Charged Particle
An ion is an atom or a group of atoms that carries an electrical charge because its number of electrons does not match its number of protons. When an atom gains one or more electrons, it acquires a net negative charge and is specifically referred to as an anion. Conversely, losing electrons leads to a positive charge, forming a cation.
The formation of ions, such as the bromide ion (Br-), is often driven by an atom’s tendency to achieve a more stable electron configuration. This stability is typically reached when an atom’s outermost electron shell is full, similar to the stable arrangement found in noble gases. The notation Br- specifically indicates that a neutral bromine atom has gained one additional electron.
The Final Count: Electrons in Br-
A neutral bromine atom contains 35 electrons. The formation of a bromide ion (Br-) signifies that the neutral bromine atom has acquired one extra electron.
To find the total number of electrons in a bromide ion, add this gained electron to the initial count. Therefore, 35 electrons + 1 electron equals 36 electrons. Consequently, a bromide ion (Br-) contains a total of 36 electrons.