The contents that follows is the substance of general sdrta.netistry class 26. In this great we proceed the conversation of Quantum Numbers and also their usage in Electron Configurations as well as the connection of electron configuration to the periodic properties the the elements.

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Electron Configuration

Electron configurations room the an introduction of where the electron are roughly a nucleus. As we learned earlier, each neutral atom has actually a number of electrons same to its variety of protons. What we will certainly do currently is location those electrons into an arrangement approximately the cell nucleus that indicates their energy and the shape of the orbital in i beg your pardon they space located. Below is a an introduction of the types of orbitals and also how numerous electrons each can contain:


So based upon what we know around the quantum numbers and using the graph above, you require 2 electron to fill an s orbital, 6 electrons to fill a ns orbital, 10 electrons to fill a d orbital and also 14 electron to to fill the f orbital. However what we haven\"t disputed is how these orbitals acquire filled...the order of fill.

Order the Fill

The bespeak in which electron are put into the orbitals is based on the order of their energy. This is referred to as the Aufbau principle. The lowest power orbitals to fill first. Just like the quantum numbers themselves this bespeak was established by calculation and is summary by the adhering to chart:


or you have the right to just usage the regular table:


How to write an Electron Configuration

The symbols used for composing the electron configuration start with the shell number (n) followed by the kind of orbital and finally the superscript suggests how many electrons space in the orbital.


For example:

Looking in ~ the regular table, you can see that Oxygen has 8 electrons. Based upon the order of fill above, these 8 electrons would fill in the following order 1s, 2s and also then 2p. Therefore Oxygen\"s electron configuration would certainly be O 1s22s22p4.

Special Cases

Configurations of ions current a special situation of electron construction and also demonstrate the reason for the development of those ion in the an initial place.

If you need to write the full electron construction for one anion, then you space just including additional electrons and also the construction is just continued.

For example, we recognize that Oxygen always forms 2- ions once it makes an ion. This would include 2 electron to its normal configuration making the new configuration: O2- 1s22s22p6. With 10 electron you should note that oxygen\"s electron construction is now exactly the very same as Neon\"s. Us talked about the fact that ions type because they deserve to become much more stable with the obtain or loss of electron to become like the noble gases and now you can actually see exactly how they end up being the same.

The electron configurations for Cations are likewise made based upon the variety of electrons however there is a slight difference in the means they room configured. An initial you must write their common electron configuration and also then once you eliminate electrons you need to take them indigenous the outermost shell. Note that this is not always the same means they were added.

Here is an example of what i mean:

Iron has 26 electron so its regular electron configuration would certainly be: Fe 1s22s22p63s23p64s23d6

When us make a 3+ ion because that Iron, we should take the electrons from the outermost shell first so that would certainly be the 4s shell NOT the 3d shell: Fe3+ 1s22s22p63s23p63d5

One other keep in mind on composing electron configurations: A short cut. Once writing some of the reduced table configurations the complete configuration deserve to be relatively long. In this cases, you can use the previous noble gas to abbreviate the configuration as presented below. Friend just have actually to finish the configuration from whereby the noble gas pipeline it:



As through every other topic we have covered to day there are exceptions to the order of fill as well. But based upon the electron configurations that are generated, these exceptions are easy to understand.

In the d block, specifically the groups containing Chromium and also Copper, there is an exception in how they are filled.

Here room the actual configurations:


In this columns, the 4s and 3d

Practice, Practice, Practice

There are lots of quizzes ~ above electron configurations you have the right to practice with located here

Orbital Diagrams

Another way to represent the stimulate of fill for an atom is by using an orbit diagram regularly referred to as \"the little boxes\":


The box are offered to stand for the orbitals and also to display the electrons put in them. The order of fill is the same yet as you deserve to see from over the electron are put singly into the boxes prior to filling them with both electrons. This is called Hund\"s Rule: \"Half fill before you full fill\" and also again this ascendancy was established based on energy calculations that shown that this to be the method atoms actually distributed their electrons into the orbitals.

Periodic Properties

One the the really cool things about electron configuration is their connection to the regular table. Basically the regular table was constructed so that elements with comparable electron configurations would be aligned into the same teams (columns).


Periodic Table mirroring last orbit filled because that each element

The routine table shown over demonstrates how the configuration of each facet was to adjust so the the critical orbital fill is the same except for the shell. The reason this to be done is that the construction of an aspect gives the aspect its properties and comparable configurations yield similar properties.

Let\"s go through few of the periodic Properties that space influenced straight by the electron configuration:

Atomic Size

The size of atoms boosts going down in the periodic table. This must be intuitive because with each row of the table friend are adding a covering (n).

What is not as intuitive is why the dimension decreases from left to right. But again the building and construction of the electron configuration provides us the answer. What space you doing as you go throughout the regular table? Answer, adding protons to the nucleus and adding electrons to the valence shell of the element. What is not transforming as you cross a period? Answer, the inner covering electrons.

So think of that this way, the inner covering electrons are a shield against the traction of the nucleus. Together you overcome a duration and increase the variety of protons in the cell core you boost its pull but due to the fact that you room only including electrons to the new shell the shield is not increasing yet remains the very same all the method across. This means the traction on the electron being included to the valence shell is increasing steadily all the means across. What wake up if you pull harder ~ above the electrons? Well, castle come closer to the nucleus and the size of the atom decreases. The result of the cell core pulling top top the electrons gift added across a duration is called the reliable nuclear charge and is calculated together ZEff = #protons - main point # Electrons.

So for example the traction felt by Sulfur would be ZEff = 16 - 10 = +6



Electronegativity might be the most essential of the routine properties you deserve to learn and understand since so many other properties are depend on the value. Electronegativity is one atoms ability to traction electrons in the direction of itself.

Electronegativity is generally expressed by the Pauling Scale and the worths were established experimentally. The table listed below shows the scale values because that the elements.


The electronegativity values boost from left come right and bottom to height in the periodic table not included the Noble gases. The most electronegative facet is Fluorine.

From these electronegativity worths we have the right to derive the patterns of two other periodic properties: Ionization Energy and also Electron Affinity.


Ionization Energy

Ionization power is the lot of power required to remove an electron from an atom. All ionization energies are positive values because all of these removals (even those for elements that form positive ions) call for input that energy. The an ext electronegative the element, the greater the ionization eneregy.

See more: Solve: 8X2 + 64X = 0. - Solve For X: 8X2 + 64X = 0

Electron Affinity

The Electron Affinity of an facet is the quantity of energy gained or released v the enhancement of an electron. The electronegativity and Electron Affinity boosts in the very same pattern in the routine table. Left to right and bottom come top.