Box Configuration

Aufbau Principle

The Aufbau principle (from the German Aufbau meaning "building up, construction") is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons. As they are added, they assume their most stable conditions (electron orbitals) with respect to the nucleus and those electrons already there.

According to the principle, electrons fill orbitals starting at the lowest available (possible) energy states before filling higher states (e.g. 1s before 2s).

A version of the Aufbau principle can also be used to predict the configuration of protons and neutrons in an atomic nucleus. 

Hund's Rule

d

Hund's Rule of Maximum Multiplicity is an observational rule which states that a greater total spin state usually makes the resulting atom more stable. The rule, discovered by Friedrich Hund in 1925, is of important use in atomic chemistry, spectroscopy, and quantum chemistry. As a result this rule is often abbreviated to Hund's Rule, ignoring the rest of Hund's Rules.

According to the principle, every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin.

Pauli's Exclusion Principle

The Pauli exclusion principle is a quantum mechanical principle formulated by the Austrian physicist Wolfgang Pauli in 1925. In its simplest form for electrons in a single atom, it states that no two electrons can have the same four quantum numbers; that is, if n, l, and m_l are the same, m_s must be different such that the electrons have opposite spins.

To be simpler, each orbital can accommodate a maximum of two electrons only if their spins are of opposite directions.

Box Configuration

An electron configuration consists of the symbol for the occupied subshell with a superscript indicating the number of electrons in the subshell. Using the Box Configuration is a way to draw the Eectron Configuration. It consists of a box representing each orbital and a half arrow representing each electron.

As shown in the image, the s subshell is assigned to only one orbital. The p is assigned to three, the d is assigned to five and the f has seven.

Each orbital, or 'box', can only have two electrons, both having different spins, shown with the up arrows and down arrows.

Exercises

Go to: Atomic Orbital Diagrams 

 

Bibliographies

http://en.wikipedia.org/wiki/Aufbau_principle

 http://en.wikipedia.org/wiki/Hund%27s_rule

http://www.chem.purdue.edu/gchelp/gloss/hundsrule.html 

http://en.wikipedia.org/wiki/Pauli_exclusion_principle 

http://www.tutorvista.com/content/chemistry/chemistry-iii/atomic-structure/electronic-configuration.php 

http://crescentok.com/staff/jaskew/ISR/chemistry/class4.htm 

 

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