chemistry - electronic structure

energy levels and sub-energy levels

Each energy level in an atom can be divided into sub-energy levels, also known as orbitals. The number of sub-energy levels within an energy level is equal to the square of the energy level. For example, the first energy level has one sub-energy level, while the second energy level has four sub-energy levels. The sub-energy levels are designated by letters (s, p, d, f) and each sub-energy level can hold a certain number of electrons.

electron configuration 3 rules

Here are the three rules for writing electron configurations:


1. Aufbau Principle: Electrons fill orbitals starting from the lowest energy level to the highest.
2. Pauli Exclusion Principle: Each orbital can hold a maximum of two electrons with opposite spins.
3. Hund's Rule: When filling orbitals with the same energy level, electrons will fill each orbital singly before pairing up.

effective nuclear charge and calculation

Effective nuclear charge is the net positive charge experienced by an electron in an atom. It is calculated by subtracting the number of shielding electrons from the total number of protons in the nucleus. The formula for effective nuclear charge is Zeff = Z - S, where Z is the atomic number and S is the number of shielding electrons. The higher the effective nuclear charge, the stronger the attraction between the nucleus and the valence electrons, which affects the atom's properties such as ionization energy and atomic radius.

strong nuclear force

The __________ is the fundamental force that holds the nucleus of an atom together by binding protons and neutrons. It is the strongest force in nature, but only operates over very short distances.

mass defect

________ is the difference between the mass of an atom and the sum of the masses of its constituent particles (protons, neutrons, and electrons).

nuclear binding energy

____________ is the amount of energy required to separate a nucleus into its individual protons and neutrons.

valence electrons

___________ are the outermost electrons in an atom that participate in chemical reactions.