describe a simple model for the nuclear atom to include protons, neutrons and orbital electrons

Simple Nuclear Atom Model ⚛️

Think of an atom as a tiny city. The nucleus is the city centre where most of the mass lives, and the electrons are like commuters moving around the streets. The nucleus contains two types of residents: protons (positively charged) and neutrons (neutral). Together they give the atom its identity and stability.

• Protons ($Z$) – give the atom its atomic number and charge.
• Neutrons ($N$) – add mass but no charge.
• Electrons ($e^-$) – orbit the nucleus and determine chemical behaviour.

The total number of nucleons (protons + neutrons) is called the mass number ($A$). It can be expressed simply as:

$$A = Z + N$$

For example, the most common hydrogen isotope has $Z=1$ and $N=0$, so $A=1$. Deuterium ($^2$H) has one neutron, giving $A=2$, and tritium ($^3$H) has two neutrons, $A=3$.

The binding energy keeps the nucleus together. A simple way to think about it is the energy required to pull the nucleus apart. The famous equation from Einstein shows the relationship between mass and energy:

$$E = mc^2$$

In nuclear physics we often use the binding energy per nucleon to compare how tightly different nuclei are held together. Higher values mean a more stable nucleus.