The contents that complies with is the problem of general stclairdrake.netistry class 26. In this great we proceed the discussion of Quantum Numbers and their usage in Electron Configurations and also the connection of electron construction to the routine properties of the elements.

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Electron Configuration

Electron configurations room the an introduction of where the electrons are roughly a nucleus. As we learned earlier, every neutral atom has a number of electrons equal to its number of protons. What we will certainly do now is ar those electrons right into an arrangement roughly the cell nucleus that suggests their energy and also the form of the orbital in which they space located. Right here is a review of the species of orbitals and also how countless electrons each have the right to contain:


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

Order of Fill

The bespeak in which electrons are put into the orbitals is based on the order of your energy. This is referred to as the Aufbau principle. The lowest power orbitals fill first. As with the quantum numbers themselves this order was determined by calculation and is summary by the adhering to chart:


or you can just usage the periodic table:


How to create an Electron Configuration

The symbols used for composing the electron configuration start with the shell number (n) adhered to by the kind of orbital and also finally the superscript shows how plenty of electrons space in the orbital.


For example:

Looking in ~ the routine table, you have the right to see that Oxygen has actually 8 electrons. Based on the order 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 certainly be O 1s22s22p4.

Special Cases

Configurations of ions current a special case of electron configuration and also demonstrate the factor for the formation of those ion in the first place.

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

For example, we know that Oxygen constantly forms 2- ions as soon as it makes an ion. This would add 2 electron to its normal configuration do the brand-new configuration: O2- 1s22s22p6. V 10 electrons you should note the oxygen"s electron configuration is now specifically the very same as Neon"s. We talked about the reality that ions kind because they deserve to become an ext stable with the obtain or ns of electron to end up being like the noble gases and now you can actually see how they come to be the same.

The electron configurations for Cations are also made based on the number of electrons however there is a slight difference in the way they are configured. An initial you must write their common electron configuration and also then once you eliminate electrons you have to take them native the outermost shell. Note that this is not constantly the same way they were added.

Here is an instance of what i mean:

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

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

One other keep in mind on writing electron configurations: A brief cut. When writing some of the lower table configurations the total configuration can be relatively long. In these cases, you deserve to use the previous noble gas to abbreviation the construction as presented below. You just have to complete the construction from whereby the noble gas leaves it:



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

In the d block, especially the teams containing Chromium and Copper, over there is an exception in exactly how they space filled.

Here are the yes, really 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 means to stand for the order of fill for one atom is by making use of an orbit diagram regularly referred to together "the tiny boxes":


The crate are offered to represent the orbitals and also to display the electrons placed in them. The stimulate of fill is the same but as you can see from above the electrons are put singly into the boxes before filling them with both electrons. This is referred to as Hund"s Rule: "Half fill before you complete fill" and again this dominance was established based on energy calculations that suggested that this to be the way atoms actually dispersed their electrons into the orbitals.

Periodic Properties

One of the really cool things around electron configuration is their connection to the regular table. Usually the routine table was built so that elements with similar electron configurations would be aligned into the same teams (columns).


Periodic Table reflecting last orbital filled for each element

The routine table shown above demonstrates how the construction of each element was aligned so that the last orbital fill is the same other than for the shell. The factor this was done is the the construction of an element gives the aspect its properties and comparable configurations yield similar properties.

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

Atomic Size

The dimension of atoms increases going down in the routine table. This need to be intuitive because with each row of the table friend are including a shell (n).

What is not as intuitive is why the size decreases from left to right. Yet again the building and construction of the electron configuration offers us the answer. What are you doing as you go across the routine table? Answer, adding protons to the cell core and adding electrons come the valence shell of the element. What is not transforming as you cross a period? Answer, the inner covering electrons.

So think of the this way, the inner shell electrons room a shield versus the traction of the nucleus. As you cross a period and rise the variety of protons in the cell core you rise its traction but because you are only including electrons come the new shell the shield is no increasing yet remains the exact same all the method across. This method the pull on the electron being included to the valence shell is enhancing steadily every the method across. What wake up if you pull harder on the electrons? Well, lock come closer come the nucleus and the dimension of the atom decreases. The effect of the cell core pulling top top the electrons gift added throughout a duration is called the efficient nuclear charge and is calculated as ZEff = #protons - core # Electrons.

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



Electronegativity may be the most crucial of the regular properties you deserve to learn and understand due to the fact that so countless other properties are rely on that is value. Electronegativity is one atoms capacity to pull electrons in the direction of itself.

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


The electronegativity values rise from left come right and bottom to peak in the routine table excluding the Noble gases. The most electronegative element is Fluorine.

From this electronegativity values we can derive the fads of two other periodic properties: Ionization Energy and Electron Affinity.


Ionization Energy

Ionization energy is the lot of energy required to eliminate an electron indigenous an atom. Every ionization energies are hopeful values because every one of these removals (even those for facets that type positive ions) need input that energy. The much more electronegative the element, the greater the ionization eneregy.

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Electron Affinity

The Electron Affinity the an aspect is the amount of power gained or released through the addition of one electron. The electronegativity and also Electron Affinity rises in the exact same pattern in the routine table. Left to right and also bottom come top.