Electronic Structure

Electronic Structure

• The electronic structure of an atom describes the arrangement of electrons in its atomic orbitals.
• Electrons inhabit areas of space known as atomic orbitals, which are each characterised by their energy levels.
• Atoms can have different numbers of electrons arranged in various energy levels or shells.

Energy Levels and Shells

• Electrons inhabit energy levels, or shells, surrounding the nucleus of an atom.
• Each energy level can hold a certain maximum number of electrons. The first energy level can hold up to 2 electrons, the second can hold up to 8, and the third can hold up to 8 as well (in most common scenarios).
• Energy levels are often represented by concentric circles around an atom’s nucleus in simplified atomic models.

Atomic Orbitals

• An orbital is a region of space around an atom’s nucleus where there’s a high probability of finding an electron.
• Different types of orbitals (s, p, d, f) have different shapes and orientations in space, and each can hold a maximum of two electrons.
• The s orbital is spherical in shape, the p orbitals are dumbbell-shaped, and d and f orbitals are more complex in shape.

Electronic Configuration

• Electronic configuration is a way of denoting the number of electrons in each energy level or shell in an atom.
• An atom’s electronic configuration can be represented using notation such as 2.2.6. This representation indicates that there are 2 electrons in the first energy level, 2 in the second, and 6 in the third.

Aufbau Principle, Pauli Exclusion Principle and Hund’s Rule

• The Aufbau Principle indicates that electrons fill atomic orbitals of the lowest available energy levels before they fill higher levels.
• The Pauli Exclusion Principle militates that each atomic orbital can hold a maximum of two electrons, and these electrons must have opposite spins.
• Hund’s Rule indicates that electrons prefer to occupy empty orbitals in the same subshell before sharing orbitals with other electrons.

Valence Electrons and Chemical Reactivity

• Valence electrons are the electrons located in the outermost shell of an atom. These electrons play a key role in chemical reactions.
• The number of valence electrons in an atom guides its chemical reactivity. Atoms tend to react to achieve a stable electron configuration similar to that of noble gases.

Understanding how the electronic structure of an atom influences chemical reactivity is crucial in the study of chemistry. This fundamental knowledge will be useful when addressing examination questions related to atomic structure and reactions.