The content that follows is the substance of general surfacetoairnewyork.comistry class 26. In this lecture we proceed the conversation of Quantum Numbers and their use in Electron Configurations and also the relationship of electron configuration to the routine properties that the elements.

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Electron Configuration

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


So based upon what we know around the quantum numbers and using the chart above, you require 2 electron to to fill an s orbital, 6 electron to fill a ns orbital, 10 electron to fill a d orbital and 14 electrons to fill the f orbital. But what we haven"t questioned is exactly how these orbitals get filled...the order of fill.

Order of Fill

The order in which electrons are placed into the orbitals is based on the order of your energy. This is referred to as the Aufbau principle. The lowest power orbitals to fill first. Similar to the quantum number themselves this order was identified by calculation and also is summarized by the following chart:


or you deserve to just use the periodic table:


How to compose an Electron Configuration

The symbols supplied for composing the electron configuration start with the covering number (n) adhered to by the type of orbital and also finally the superscript shows how numerous electrons space in the orbital.


For example:

Looking in ~ the routine table, you deserve to see that Oxygen has 8 electrons. Based on the stimulate of to fill above, these 8 electrons would fill in the adhering to order 1s, 2s and then 2p. For this reason Oxygen"s electron configuration would certainly be O 1s22s22p4.

Special Cases

Configurations the ions present a special instance of electron construction and also demonstrate the factor for the development of those ion in the an initial place.

If you have to write the full electron configuration for an anion, climate you room just adding additional electrons and the configuration is simply continued.

For example, we recognize that Oxygen always forms 2- ions when it provides an ion. This would include 2 electrons to its regular configuration do the brand-new configuration: O2- 1s22s22p6. V 10 electron you should note the oxygen"s electron configuration is now specifically the exact same as Neon"s. Us talked about the reality that ions form because they can become an ext stable through the acquire or ns of electron to end up being like the noble gases and also now you have the right to actually see how they come to be the same.

The electron configurations because that Cations are likewise made based upon the number of electrons yet there is a slight distinction in the means they room configured. Very first you have to write their regular electron configuration and then once you remove electrons you need to take them from the outermost shell. Note that this is not always the same way they were added.

Here is an instance of what i mean:

Iron has actually 26 electrons so its typical electron configuration would be: Fe 1s22s22p63s23p64s23d6

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

One other note on writing electron configurations: A brief cut. As soon as writing some of the lower table construction the full configuration have the right to be relatively long. In this cases, you have the right to use the vault noble gas to abbreviation the configuration as presented below. Friend just have to end up the construction from whereby the noble gas pipeline it:



As with every other topic we have covered to day there space exceptions come the bespeak of fill as well. But based on the electron configuration that space generated, this exceptions are easy to understand.

In the d block, specifically the teams containing Chromium and Copper, over there is an exemption in just how they room filled.

Here are the actual configurations:


In these columns, the 4s and 3d

Practice, Practice, Practice

There are lots of quizzes top top electron configurations you can practice with situated here

Orbital Diagrams

Another means to stand for the order of fill for an atom is by using an orbit diagram regularly referred to together "the small boxes":


The box are used to represent the orbitals and also to display the electrons put in them. The order of to fill is the same but as you have the right to see from over the electrons are inserted singly right into the boxes prior to filling them through both electrons. This is referred to as Hund"s Rule: "Half fill prior to you complete fill" and also again this preeminence was established based on energy calculations that indicated that this was the way atoms actually spread their electrons into the orbitals.

Periodic Properties

One the the really cool things around electron configuration is their partnership to the routine table. Basically the regular table was constructed so that facets with comparable electron configurations would certainly be aligned into the same groups (columns).


Periodic Table mirroring last orbital filled for each element

The regular table shown above demonstrates how the configuration of each element was set so the the critical orbital filled is the same other than for the shell. The factor this to be done is that the configuration of an aspect gives the facet its properties and similar configurations yield comparable properties.

Let"s go through several of the routine Properties that room influenced straight by the electron configuration:

Atomic Size

The dimension of atoms rises going under in the regular table. This have to be intuitive due to the fact that with each heat of the table girlfriend are adding a shell (n).

What is no as intuitive is why the dimension decreases indigenous left come right. Yet again the building of the electron configuration gives us the answer. What room you doing together you go throughout the regular table? Answer, including protons to the cell core and including electrons come the valence covering of the element. What is not an altering as you overcome a period? Answer, the inner covering electrons.

So think of it this way, the inner shell electrons are a shield against the pull of the nucleus. Together you cross a duration and rise the number of protons in the cell nucleus you boost its pull but since you space only including electrons come the new shell the shield is no increasing but remains the exact same all the method across. This method the traction on the electrons being added to the valence covering is increasing steadily all the means across. What happens if you traction harder top top the electrons? Well, they come closer come the nucleus and the size of the atom decreases. The impact of the cell core pulling ~ above the electrons gift added across a period is dubbed the reliable nuclear charge and also is calculated together ZEff = #protons - core # Electrons.

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



Electronegativity may be the most necessary of the periodic properties you can learn and also understand since so many other nature are rely on its value. Electronegativity is an atoms capacity to pull electrons in the direction of itself.

Electronegativity is typically expressed through the Pauling Scale and the worths were identified experimentally. The table listed below shows the scale values for the elements.


The electronegativity values boost from left come right and also bottom to top in the periodic table not included the Noble gases. The many electronegative element 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 amount of power required to remove an electron indigenous an atom. All ionization energies are optimistic values because every one of these removals (even those for aspects that kind positive ions) call for input that energy. The much more electronegative the element, the higher the ionization eneregy.

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Electron Affinity

The Electron Affinity of an aspect is the quantity of energy gained or released through the enhancement of an electron. The electronegativity and also Electron Affinity increases in the same pattern in the routine table. Left come right and bottom come top.