The phrase “give the nuclear symbol for the isotope of bromine” points to nuclide notation, written as \(^{A}_{Z}\text{Br}\), where \(Z\) is the atomic number (protons) and \(A\) is the mass number (protons + neutrons). Bromine has \(Z=35\), so every bromine isotope has 35 protons and differs only in neutron number \(N\).
Nuclide notation for bromine
The neutron number follows \(N=A-Z\). Naturally occurring bromine is commonly represented by its two stable isotopes, bromine-79 and bromine-81, so both nuclear symbols are standard in general chemistry contexts.
Meaning of the numbers in \(^{A}_{Z}\text{Br}\)
Atomic number (Z) equals the number of protons in the nucleus and defines the element. Bromine is always \(Z=35\).
Mass number (A) equals total nucleons (protons + neutrons). Different isotopes have different \(A\).
Neutron number (N) equals \(A-Z\) and changes from isotope to isotope.
Summary table for bromine isotopes
| Isotope name | Nuclear symbol | Atomic number \(Z\) (protons) | Mass number \(A\) | Neutrons \(N=A-Z\) |
|---|---|---|---|---|
| Bromine-79 | \(^{79}_{35}\text{Br}\) | 35 | 79 | \(79-35=44\) |
| Bromine-81 | \(^{81}_{35}\text{Br}\) | 35 | 81 | \(81-35=46\) |
Other bromine isotopes (radioisotopes) follow the same nuclear-symbol pattern, such as \(^{82}_{35}\text{Br}\) or \(^{77}_{35}\text{Br}\), with neutron number given by \(N=A-35\).