According to the Aufbau principle, which orbital is filled immediately before each of the following? (a) 3p (b) 4p (c) 4f (d) 5d

The Aufbau principle states that electrons occupy the lowest energy orbitals first before moving to higher energy levels. This principle guides the order in which atomic orbitals are filled, ensuring that the most stable electron configuration is achieved. Understanding this principle is crucial for predicting the electron configuration of elements in the periodic table.

Orbital energy levels refer to the different energy states that electrons can occupy within an atom. These levels are organized in a specific order based on their energy, with s, p, d, and f orbitals having increasing energy levels. Familiarity with these energy levels helps in determining which orbitals are filled in accordance with the Aufbau principle.

Electron configuration describes the distribution of electrons in an atom's orbitals. It is represented using a notation that indicates the energy levels and types of orbitals occupied by electrons. Knowing how to write and interpret electron configurations is essential for understanding chemical properties and reactivity of elements.