What does the Aufbau principle state about the addition of protons and electrons to form new elements?

The Aufbau principle explains the process of building up electron configurations in atoms as protons are added to the nucleus. Specifically, it states that as protons are added to the nucleus of an atom to form a new element, electrons are also added to the electron cloud surrounding the nucleus. Each element corresponds to a specific atomic number, which is the number of protons in the nucleus. Correspondingly, to maintain charge neutrality, the same number of electrons must be present. Therefore, when a new proton is introduced as an atomic number increases, an electron is added to the outer shell in accordance with the order of increasing energy levels.

This principle is key to understanding how the electronic structure of elements behaves in relation to their nuclear charge. The other choices do not accurately reflect the relationship between protons and electrons: subtracting electrons when protons are added, stating that protons and electrons remain constant, or implying that electrons are only added under specific conditions are inconsistent with the basic understanding of atomic theory as outlined by the Aufbau principle.