Electron Arrangement

Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), Jen Moreau


About Electron Arrangement

This topic often confuses people so don't worry if you don't understand it first time. Read up on electron arrangement in textbooks and get other people to explain it to you. Before this level of study you will have been told that electrons have fields of 2,8,8 maximum capacity. Well, this is not true. As well as main energy levels, there are also sub-shells. The table below outlines this information.

Was this helpful? Yes | No | I need help
Main Level Sub-level Electron capacity
1 s 2
2 s 2
p 6
3 s 2
p 6
d 10

For these sub-shells, it's important to note that the 4S requires less energy for electrons to enter it, than the 3d. Other than this, the electrons fill up each successive sub shell in order to form electrons. Below are the electron configurations of some elements.

Was this helpful? Yes | No | I need help

some electron configurations

Highlighted on the image are two features:

  1. 1
    Scandium (Sc)
    At Scandium, the electrons in 3d start to fill up after 4S.
    Was this step helpful? Yes | No | I need help
  2. 2
    Electronic Configuration [Ne]
    The second is [Ne], this is a shorthand way of writing the electronic configuration. the bit highlighted means the electron configuration of Neon then the rest. You can use any noble gas, dependent on its size.
    Was this step helpful? Yes | No | I need help

Hund's Maximum Multiplicity Rule

This rule is an important one when considering electron arrangement and ionization energy. It states that in subshells, the electrons will as fill singly as much a possible, before doing so in pairs. This is to be as energy efficient as possible. It is demonstrated below using spin diagrams.

Was this helpful? Yes | No | I need help
hunds rule of maximum multiplicity

Ionization Energy

The first ionization energy is defined as: The energy/enthalpy change when one mole of electrons is removed from one mole of a gaseous element, the equations for the first and second ionization energies are shown below.

Was this helpful? Yes | No | I need help
equations for the first and second ionisation energies

The ionization energies of elements have a distinctive pattern, which provides evidence for the structure of electrons explained above.

Group II patterns

first ionisation energies of group 2 elements

Down the groups there is a decrease in first ionization energy. This is because of the following factors:

  1. 1
    Atomic Radius
    This is the distance of the outermost electron to the nucleus. As you go down the groups, this distance gets bigger, so it becomes easier to remove electrons (less energy is required) as they are further from the attractive force of the nucleus.
    Was this step helpful? Yes | No | I need help
  2. 2
    Electron Shielding
    As you go down the group there is a new n (main) electron level. This means that other electrons are below the outermost. Because of this, there is a degree of repulsion, which means the electron is more readily lost.
    Was this step helpful? Yes | No | I need help

Period III Patterns

first ionisation energies of period 3 elements

The pattern of first ionization energies across a period is a little more complex because it doesn't show a perfect pattern. However, there is a general increase along the period because of increasing nuclear charge. The force of attraction from the increasing number of protons means the electrons are being held in place with more force so more energy is required to remove them.

Was this helpful? Yes | No | I need help

There is a drop in first ionization energy from magnesium to aluminium. This is because from Al, the electrons start filling the 3p sub-shell, and because this is in a higher energy level, it is lower.

Was this helpful? Yes | No | I need help

The next slight fall is from Phosphorus to Sulphur. This is because of Hund's maximum multiplicity as explained above. The electrons begin to pair up, and so less energy is required to remove it since the two electrons in a pair repel each other slightly.

Was this helpful? Yes | No | I need help

Referencing this Article

If you need to reference this article in your work, you can copy-paste the following depending on your required format:

APA (American Psychological Association)
Electron Arrangement. (2017). In ScienceAid. Retrieved Apr 27, 2017, from https://scienceaid.net/chemistry/fundamental/electrons.html

MLA (Modern Language Association) "Electron Arrangement." ScienceAid, scienceaid.net/chemistry/fundamental/electrons.html Accessed 27 Apr 2017.

Chicago / Turabian ScienceAid.net. "Electron Arrangement." Accessed Apr 27, 2017. https://scienceaid.net/chemistry/fundamental/electrons.html.

If you have problems with any of the steps in this article, please ask a question for more help, or post in the comments section below.


ScienceAid welcomes all comments. If you do not want to be anonymous, register or log in. It is free.

Ask the author

Featured Author
166 Articles Started
1,284 Article Edits
43,715 Points
Jamie is a featured author with ScienceAid. Jamie has achieved the level of "Captain" with 43,715 points. Jamie has started 166 articles (including this one) and has also made 1,284 article edits. 103,000 people have read Jamie's article contributions.
Jamie's Message Board
Jamie: Hi, my name is Jamie.
Jamie: Can I help you with your problem about "Electron Arrangement"?

Article Info

Categories : Fundamental

Recent edits by: Taylor (ScienceAid Editor), Jamie (ScienceAid Editor)

Share this Article:

Thanks to all authors for creating a page that has been read 722 times.

Do you have a question not answered in this article?
Click here to ask one of the writers of this article

Thank Our Volunteer Authors.

Would you like to give back to the community by fixing a spelling mistake? Yes | No