The strong nuclear force is indeed a very strong force that binds protons and neutrons together in the atomic nucleus. It is responsible for overcoming the electrostatic repulsion between positively charged protons, keeping the nucleus stable. However, the reason atoms are not just one massive nucleus with all the electrons orbiting around it lies in the interplay of different forces and quantum mechanics.
In an atom, the electrons are not only influenced by the attractive force of the nucleus (dominated by the strong nuclear force) but also by the electromagnetic force. The electromagnetic force arises from the interaction between charged particles, and it acts between the negatively charged electrons and the positively charged protons.
The behavior of electrons is described by quantum mechanics, and it introduces the concept of quantization and wave-particle duality. According to quantum mechanics, electrons exist in quantized energy levels or orbitals around the nucleus. These orbitals represent the probability distribution of finding an electron at different positions around the nucleus.
The electrons occupy specific orbitals depending on their energy levels and quantum numbers. The lowest energy level orbitals, known as the 1s orbital, can hold a maximum of two electrons. As you move to higher energy levels, the number of possible orbitals and the maximum number of electrons per orbital increases.
The electromagnetic force between electrons and the positively charged nucleus determines the electron's energy levels and their arrangement in orbitals. Atoms strive for stability and tend to have the lowest energy configuration possible, known as the ground state. This configuration involves electrons filling orbitals in a specific order according to the Aufbau principle, Pauli exclusion principle, and Hund's rule.
So, while the strong nuclear force is indeed strong, the electromagnetic force and the quantum mechanical behavior of electrons prevent the electrons from simply collapsing into the nucleus. The balance between these forces and the quantized nature of electron energy levels give rise to the complex structure of atoms, where electrons occupy specific orbitals at various distances from the nucleus.