Understood. My apologies for the repetition. Let's proceed to the next topic. The next concept is Electron Configuration. Electron configuration describes the arrangement of electrons in an atom's electron shells and subshells. Electrons occupy specific energy levels and orbitals around the nucleus. The rules for electron configuration include: 1. The Aufbau Principle: Electrons fill the lowest energy orbitals first. 2. The Pauli Exclusion Principle: An orbital can hold a maximum of two electrons, and they must have opposite spins. 3. Hund's Rule: Electrons will individually occupy orbitals within a subshell before pairing up. The order of filling orbitals is typically: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on. For example, the electron configuration of Oxygen (atomic number 8) is 1s²2s²2p⁴. This means it has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, and 4 electrons in the 2p orbitals.