When an atom has no net charge, it means that the number of protons in its nucleus is equal to the number of electrons surrounding the nucleus. In this balanced state, the electrons are distributed in specific energy levels or orbitals around the nucleus.
Electrons in an atom follow the principles of quantum mechanics, which describe their behavior in terms of wave functions and probabilities. Each energy level or orbital can accommodate a specific number of electrons. The closest energy level to the nucleus, called the 1s orbital, can hold up to two electrons. The next energy level, the 2s orbital, can also hold up to two electrons. The 2p orbital, which is at a slightly higher energy, can accommodate up to six electrons (two in each of the three available p orbitals).
To achieve a no net charge state, the electrons fill these orbitals starting from the lowest energy level. This filling pattern follows the "aufbau principle," which states that electrons occupy the lowest available energy levels before occupying higher levels.
For example, let's consider a carbon atom with atomic number 6. Carbon has six electrons, and in its neutral state, it has the following electron configuration:
1s^2 2s^2 2p^2
This means that the first energy level (1s) is fully occupied with two electrons, and the second energy level (2s and 2p) is also filled with four electrons (two in the 2s orbital and two in the 2p orbital). Since the number of protons (which determines the atomic number and element) is equal to the number of electrons, the atom has no net charge.
In summary, when an atom has no net charge, the electrons are distributed in energy levels and orbitals around the nucleus according to specific rules and principles, resulting in a balanced state where the number of electrons equals the number of protons.