The content that adheres to is the problem of general ivorycrimestory.comistry class 26. In this lecture we proceed the discussion of Quantum Numbers and also their usage in Electron Configurations and the connection of electron configuration to the routine properties that the elements.

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Electron Configuration

Electron configurations are the review of wherein the electron are roughly a nucleus. Together 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 into an arrangement about the cell nucleus that indicates their energy and the form of the orbital in which they are located. Right here is a review of the species of orbitals and also how many electrons each deserve to contain:


So based on what we know about the quantum numbers and using the graph above, you require 2 electron to to fill an s orbital, 6 electrons to fill a ns orbital, 10 electrons to to fill a d orbital and 14 electron to fill the f orbital. Yet what us haven"t discussed is exactly how these orbitals gain filled...the stimulate of fill.

Order of Fill

The order in which electron are placed into the orbitals is based upon the order of your energy. This is referred to as the Aufbau principle. The lowest energy orbitals fill first. Similar to the quantum numbers themselves this order was figured out by calculation and is summary by the following chart:


or you have the right to just use the routine table:


How to create an Electron Configuration

The symbols used for creating the electron configuration start with the shell number (n) complied with by the kind of orbital and finally the superscript suggests how numerous electrons are in the orbital.


For example:

Looking in ~ the regular table, you deserve to see the Oxygen has actually 8 electrons. Based upon the stimulate of fill above, these 8 electrons would fill in the following order 1s, 2s and also then 2p. For this reason Oxygen"s electron configuration would be O 1s22s22p4.

Special Cases

Configurations that ions current a special instance of electron construction and additionally demonstrate the factor for the development of those ions in the very first place.

If you must write the complete electron construction for an anion, climate you space just including additional electrons and the construction is merely continued.

For example, we know that Oxygen always forms 2- ions as soon as it makes an ion. This would add 2 electron to its common configuration making the new configuration: O2- 1s22s22p6. With 10 electrons you need to note the oxygen"s electron construction is now precisely the very same as Neon"s. We talked around the fact that ions type because they can become more stable through the acquire or loss of electron to come to be like the noble gases and now you deserve to actually see just how they become the same.

The electron configurations because that Cations are likewise made based upon the variety of electrons yet there is a slight difference in the means they space configured. Very first you have to write their typical electron configuration and then when you eliminate electrons you need to take them from the outermost shell. Keep in mind that this is not always the same method they to be added.

Here is an instance of what i mean:

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

When we make a 3+ ion for Iron, we need to take the electrons from the outermost shell an initial so that would be the 4s shell NOT the 3d shell: Fe3+ 1s22s22p63s23p63d5

One other keep in mind on writing electron configurations: A quick cut. Once writing few of the lower table configurations the full configuration have the right to be relatively long. In these cases, you have the right to use the ahead noble gas to abbreviate the construction as presented below. You just have actually to finish the configuration from where the noble gas leaves it:



As through every other topic we have covered to date there room exceptions come the order of fill as well. But based upon the electron configuration that room generated, this exceptions are basic to understand.

In the d block, especially the teams containing Chromium and also Copper, there is an exemption in exactly how they are filled.

Here are the really configurations:


In these columns, the 4s and 3d

Practice, Practice, Practice

There are lots of quizzes top top electron configuration you have the right to practice with located here

Orbital Diagrams

Another way to stand for the bespeak of fill for one atom is by utilizing an orbital diagram regularly referred to as "the small boxes":


The crate are offered to represent the orbitals and to show the electrons put in them. The order of fill is the same however as you have the right to see from above the electron are inserted singly right into the boxes before filling them v both electrons. This is called Hund"s Rule: "Half fill prior to you complete fill" and also again this rule was established based upon energy calculations that shown that this to be the method atoms actually distributed their electrons right into the orbitals.

Periodic Properties

One that the yes, really cool things around electron configurations is their relationship to the regular table. Basically the routine table was built so that aspects with comparable electron configurations would be aligned into the same teams (columns).


Periodic Table mirroring last orbital filled because that each element

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

Let"s go through some of the regular Properties that space influenced straight by the electron configuration:

Atomic Size

The dimension of atoms increases going down in the routine table. This need to be intuitive due to the fact that with each heat of the table friend are adding a shell (n).

What is not as intuitive is why the dimension decreases native left come right. However again the building of the electron configuration provides us the answer. What room you doing together you go across the regular table? Answer, including protons come the cell nucleus and adding electrons come the valence covering of the element. What is not an altering as you cross a period? Answer, the inner shell electrons.

So think of the this way, the inner shell electrons are a shield versus the pull of the nucleus. As you overcome a period and rise the number of protons in the cell nucleus you increase its pull but since you room only adding electrons come the new shell the shield is no increasing but remains the very same all the method across. This method the pull on the electrons being added to the valence shell is increasing steadily all the means across. What wake up if you traction harder on the electrons? Well, lock come closer come the nucleus and the size of the atom decreases. The impact of the cell core pulling on the electrons being added across a duration is called the reliable nuclear charge and also is calculated as ZEff = #protons - main point # Electrons.

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



Electronegativity may be the most important of the regular properties you have the right to learn and understand because so numerous other properties are rely on its value. Electronegativity is one atoms capability to pull electrons towards itself.

Electronegativity is usually expressed through the Pauling Scale and also the worths were determined experimentally. The table below shows the range values for the elements.


The electronegativity values boost from left to right and also bottom to peak in the periodic table excluding the Noble gases. The most electronegative element is Fluorine.

From these electronegativity values we have the right to derive the trends 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 indigenous an atom. All ionization energies are hopeful values because all of these removals (even those for aspects that kind positive ions) require input that energy. The more electronegative the element, the higher the ionization eneregy.

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Electron Affinity

The Electron Affinity the an element is the lot of energy gained or released v the enhancement of an electron. The electronegativity and also Electron Affinity rises in the same pattern in the regular table. Left come right and bottom come top.