Key Concepts: Electronic Configurations

Key Concepts: Electronic Configurations

  • The electron configuration of an atom in its ground state describes the distribution of electrons into energy levels or “shells”. This pattern is crucial to understand how elements react chemically.

  • The first shell, closest to the nucleus, can hold up to 2 electrons. Further shells can hold up to 8 electrons.

  • Electrons tend to occupy the lowest possible energy levels available and are distributed from the innermost shell outward.

  • Each electron in an atom has its specific place in a shell, described by quantum numbers. This is based on the principle of quantum mechanics.

  • The order in which the shells fill is not always sequential. After the first 20 elements, electrons start filling higher energy levels before the lower ones are full.

  • The period number in the periodic table indicates the number of shells of electrons an element has.

  • Group number in the periodic table (for groups 1 to 8) often indicates the number of electrons in the outer shell.

  • Elements in the same group have the same number of electrons in their outer shell, hence exhibit similar chemical properties.

  • The noble gases, found in group 8 (or 0), have full outer electron shells (either two or eight electrons). They are generally very stable and do not readily react to form compounds.

  • Valence electrons, electrons in the outermost shell, are most involved in chemical reactions.

  • Elements strive to have their outer shell full, to reach a more stable configuration. This drive determines the chemical reactivity and bonding characteristics of an element.

  • Ionic bonding involves the transfer of electrons from one atom to another, resulting in ions with full outer shells.

  • Covalent bonding, on the other hand, involves sharing of electrons between atoms to achieve a fully-filled outer shell.

  • Electron configuration plays a critical role in predicting the physical properties of metals and non-metals. For example, metals, which tend to lose electrons, are good conductors of electricity while non-metals, which tend to gain or share electrons, act as insulators.

  • Knowledge of electron configuration can also assist in understanding the trends seen across the periodic table in terms of reactivity, atomic radius, ionisation energy, and electron affinity.