Electronic Configurations

An electronic configuration is a description of which orbitals in an atom contain electrons and how many electrons are in each orbital

Aufbau Principal

As the atomic number increases, electrons are added to the available orbitals. Electrons are added to the orbitals having the lowest energy first.

Hund’s Principle

Orbitals of equal energy are each occupied by one electron before any pairing of electrons occur

Pauli Exclusion Principle

Each orbital can contain only a massive amount of two electrons with opposite spins

2 electrons in an s-type subshell

6 electrons in a p-type subshell

10 electrons in a d-type subshell

14 electrons in an f-type subshell

Orbitals

Core Notation

The core of an atom is the set of electrons with the configuration of the previous noble gas, having an atomic number less than that of the atom being considered

Rules for Core Notation

1. Locate the atom and note the noble gas at the end of the row above the element.

2. Start to write the electron configuration as usual replace a part of the electron configuration corresponding The configuration of the noble gas with the symbol for the noble gas in square brackets. Followed the Core symbol with the electronic configurations of the remaining outer electrons.

Ex. [Noble Gas] + Extra Orbitals

Exceptions

Chromo and copper, because half filled and filled orbitals are more favourable

Electron Configurations for Anions

Add electrons equal to a charge to the last unfilled subshell, starting with the Neutral atom left off

Electron configurations for Cations

1. starting with the neutral configuration in core notation, removes electrons from the outermost shell the largest energy level first

2. If there are electrons in both the S and P orbitals of the outermost shell, the electrons in the P orbitals are removed first

Summary: P than S than D than F

Valence electrons

Valence electrons are all the electrons in the atom EXCEPT those in the

- [core]

- filled D and F sub shells

* if it’s unfilled, ‘F + D’ then it’s part of the valance

* If you can make something helpful or filled, do it

*S+P UNLESS P is filled