CIR Rm.5

Box Configuration
- ways in which electrons are arranged around the nuclei of atoms

1. Aufbau Principle

It is a principle in which an atom is “built up” by adding together electrons. This is used to know the electron configuration of an atom, molecule or ion. Electrons fill orbitals beginning at the lowest free possible energy states before filling higher states.

It is also known as "constructing a building". It starts from the lowest to the highest energy level. It follows the ruling or order of the Mnemonic device.

Mnemonics
The Mnemonic device is composed of the s, p, d and f.

S stands for Sharp (sphere) which contains a maximum of 2 electrons.
P stands for Principal (clover) which contains a maximum of 6 electrons.
D stands for Diffused (dumbbell) which contains a maximum of 10 electrons.
F stands for Fundamental (undefined) which contains a maximum of 14 electrons.

principle quantum number	number of subshells	the subshell labels
1	1	s
2	2	s,p
3	3	s,p,d
4	4	s,p,d,f

2. Pauli's Exclusion

It is a principle that states that no 2 electrons could possibly have the same 4 quantum numbers. If n, l, and m¹ are identical, m² must be different thus having opposite spins. It also states that an atomic orbital may describe at most two electrons.

Quantum Numbers

This is where the Quantum Numbers enter. Quantum Numbers are numbers that represent on how you will find a certain electron.

Nitrogen - 1s² 2s² 2p³

1. n

N represents the principle quantum number. It is the last number found in the electron configuration.
In the given element, n will be 2 because the last number found in the electron configuration is 2, from 2p³.

2. l

L represents the azimuthal quantum number. It is used to determine in which orbital the given electron is placed.
The equivalents of each Mnemonic are the following: s = 0, p = 1, d = 2, & f = 3.
In the given element, l will be 1 because the last letter found in the electron configuration is p and p is represented by the number 1.

3. m¹

M¹ represents the magnetic quantum number. It enables us to determine at what box the given electron is located.

In the figure above, you can see the different numbers representing each box per each orbital. S only has one box which gives a number represented by 0. P can either be -1, 0, or 1, depending on the given electron. D can range from -2 to +2 and f can range from -3 to +3.
In the given element, m1 will be 1 because the 3rd arrow is placed in the 3rd box which is represented by the number 1.

4. m²

M² represents the magnetic spin of the electron. It can either be + 1/2 or - 1/2. +1/2 is determined by a positive electron or an electron having a clockwise spin of direction. It is represented by an arrow pointing upwards. On the other hand, -1/2 is determined by a negative electron having a counter clockwise spin of direction. It is represented by an arrow pointing downwards.
In the given element, m² will be +1/2 because the last arrow placed in the boxes is pointing up.

Box Configuration

It is a system used to determine the place of the electrons. It is an electronic configuration described by box notation form i.e., putting an arrow for single electron in a box or a pair of arrows for two electrons in a box. The direction of the arrows gives the orientation of its spin.

Examples:

3. Hund's Rule

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. In short, when electrons occupy orbitals of equal energy, one electron enters each orbital until all orbitals contain one electron with parallel spins.

They occupy each room first with 1 positive spin that should fill up all the boxes in one orbital and once they are completed, that's the time when the negative spins will go with the positive spins.