The content that follows is the problem of basic ubraintv-jp.comistry great 26. In this class we proceed the conversation of Quantum Numbers and also their use in Electron Configurations as well as the partnership of electron configuration to the periodic properties that the elements.

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Electron Configuration

Electron configurations space the summary of wherein the electron are roughly a nucleus. Together we learned earlier, every neutral atom has actually a variety of electrons equal to its number of protons. What we will do currently is ar those electrons into an arrangement roughly the nucleus that suggests their energy and also the form of the orbital in which they space located. Here is a an introduction of the varieties of orbitals and also how plenty of electrons each can contain:


So based on what we know around the quantum numbers and also using the chart above, you need 2 electrons to fill an s orbital, 6 electron to fill a ns orbital, 10 electrons to to fill a d orbital and also 14 electron to fill the f orbital. However what we haven"t discussed is exactly how these orbitals gain filled...the order of fill.

Order the Fill

The bespeak in which electron are placed into the orbitals is based upon the bespeak of their energy. This is described as the Aufbau principle. The lowest power orbitals fill first. As with the quantum number themselves this stimulate was established by calculation and is summary by the complying with chart:


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


How to write an Electron Configuration

The symbols provided for composing the electron configuration start with the shell number (n) complied with by the form of orbital and also finally the superscript suggests how many electrons room in the orbital.


For example:

Looking at the routine table, you deserve to see the Oxygen has 8 electrons. Based upon the order of fill above, this 8 electrons would fill in the following order 1s, 2s and then 2p. So Oxygen"s electron configuration would certainly be O 1s22s22p4.

Special Cases

Configurations that ions existing a special case of electron construction and likewise demonstrate the factor for the development of those ion in the very first place.

If you should write the complete electron configuration for one anion, then you room just adding additional electrons and the construction is merely continued.

For example, we understand that Oxygen constantly forms 2- ions once it renders an ion. This would add 2 electrons to its normal configuration do the new configuration: O2- 1s22s22p6. V 10 electrons you must note the oxygen"s electron configuration is now exactly the same as Neon"s. Us talked about the fact that ions kind because they can become an ext stable through the obtain or ns of electron to become like the noble gases and now you deserve to actually see how they come to be the same.

The electron configurations because that Cations are additionally made based on the number of electrons but there is a slight difference in the means they are configured. An initial you need to write their normal electron configuration and also then once you eliminate electrons you have to take them indigenous 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 26 electron so its common electron configuration would be: Fe 1s22s22p63s23p64s23d6

When we make a 3+ ion for 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 note on writing electron configurations: A short cut. When writing some of the lower table configurations the full configuration can be relatively long. In these cases, you deserve to use the previous noble gas to abbreviate the construction as presented below. Friend just have to finish the configuration from where the noble gas leaves it:



As with every other topic we have covered to date there are exceptions to the stimulate of fill together well. But based upon the electron construction that space generated, this exceptions are basic to understand.

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

Here room the actual configurations:


In these columns, the 4s and also 3d

Practice, Practice, Practice

There are lots of quizzes on electron configuration you deserve to practice with situated here

Orbital Diagrams

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


The box are supplied to represent the orbitals and to present the electrons put in them. The stimulate of fill is the same yet as you have the right to see from above the electrons are inserted singly right into the boxes before filling them with both electrons. This is referred to as Hund"s Rule: "Half fill prior to you complete fill" and also again this dominance was established based upon energy calculations that indicated that this was the method atoms actually dispersed their electrons into the orbitals.

Periodic Properties

One that the really cool things about electron construction is their partnership to the regular table. Basically the regular table was created so that elements with similar electron configurations would certainly be aligned right into the same teams (columns).


Periodic Table mirroring last orbit filled because that each element

The periodic table shown over demonstrates how the construction of each facet was aligned so the the last orbital fill is the same except for the shell. The factor this was done is that the configuration of an aspect gives the aspect its nature and similar configurations yield comparable properties.

Let"s walk through some of the routine Properties that space influenced directly by the electron configuration:

Atomic Size

The size of atoms boosts going down in the routine table. This need to be intuitive because with each row of the table girlfriend are adding a covering (n).

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

So think of that this way, the inner covering electrons space a shield against the traction of the nucleus. As you cross a duration and boost the variety of protons in the cell nucleus you boost its traction but since you room only including electrons come the new shell the shield is not increasing however remains the same all the method across. This method the traction on the electron being added to the valence shell is enhancing steadily all the way across. What wake up if you traction harder on the electrons? Well, castle come closer to the nucleus and also the size of the atom decreases. The result of the cell nucleus pulling ~ above the electrons being added across a duration is referred to as the effective nuclear charge and also is calculated as ZEff = #protons - main point # Electrons.

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



Electronegativity may be the most important of the regular properties you can learn and also understand because so numerous other nature are count on the value. Electronegativity is an atoms capacity to pull electrons in the direction of itself.

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


The electronegativity values rise from left come right and also bottom to height in the periodic table not included the Noble gases. The many electronegative element is Fluorine.

From this electronegativity values we have the right to derive the trends of two various other periodic properties: Ionization Energy and also Electron Affinity.


Ionization Energy

Ionization energy is the lot of energy required to remove an electron indigenous an atom. Every ionization energies are hopeful values because all of these removals (even those for elements that type positive ions) need input the energy. The an ext electronegative the element, the higher the ionization eneregy.

See more: Q: Is 29 A Prime Or Composite Number ? Q: Is 29 A Composite Number

Electron Affinity

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