Atomic structure and electron configuration

Atoms consist of a positively charged nucleus containing protons and neutrons, surrounded by negatively charged electrons. The electrostatic interactions between these charged particles, described by Coulomb's law, determine how tightly the electrons are held.

F ∝ (q₁ q₂)/r²

Nuclear Charge, Distance, and Shielding

• A greater nuclear charge increases the attractive force on the electrons
• A greater distance from the nucleus and increased shielding by core electrons decrease this force

These relationships are the foundation for understanding electron configurations, ionization energy trends, and the differences between core and valence electrons.

Electron Configuration

• Electrons occupy shells and subshells in order of increasing energy, following the Aufbau principle, which produces the ground-state electron configuration
• Inner electrons are called core electrons
• Outermost-shell electrons are called valence electrons
• When forming cations, electrons are removed from the highest principal energy level (largest n) first

Ionization Energy

Key Definition Ionization energy is the energy required to remove an electron from a gaseous atom or ion in its ground state.

• It increases with increasing effective nuclear charge
• It decreases as the distance of the electron from the nucleus increases
• A large jump between successive ionization energies signals the transition from removing valence electrons to removing core electrons

Qualitative application of Coulomb's law explains these energy differences across atoms, ions, and subshells.