Electron configuration

Distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals is known as electron configuration. It packs in a little space having a lot of data and it requires a little exercise to read.  For example, this is the electron configuration for oxygen,


Electron configuration

What is meaning of all those numbers and letters?

Each row of a table for electron configuration is like a phrase. Every ‘ sentence ‘ consists of smaller ‘ words. ‘ This format follows every ‘ word ‘:

Electron configuration

The first number is the energy level. The lowercase letter is the sub-shell. The number in superscript is the number of electrons in a sub-shell.

The small superscripts tell how many electrons live in each orbital, the letters represent the available orbitals, and the large numbers indicate the amount of energy discovered in the orbitals. Recall that the complete amount of electrons is equal to the complete amount of protons, so the superscripts add up to 8, the oxygen atomic number. There are up to four distinct orbitals accessible for each power level, but the amount of electrons that can live in each orbital varies based on the type:

  1. Only two occupants can be held in the efficiency suite, denoted by s.
  2. The normal size, p, can hold up to six inhabitants. Because in oxygen atoms there are only eight electrons searching for homes, this apartment has only four residents in oxygen, so there are two additional places available for any chemical reactions where oxygen gains electrons.
  3. Some of the bigger houses on the periphery of the park may have even bigger apartments accessible, d (10 electrons) and f (14 electrons), but usually you’ll only meet these people when you’re really far down the regular table, so there’s plenty of electrons searching for homes.
Electron configuration

It turns out that there are even more complicated rules to determine which electrons end up in which orbitals as you move further down the periodic table, as subtle effects due to quantum mechanics can encourage electrons to select apartments further out of the nucleus even when openings are available in closer apartments. But two general trends remain the same: electrons want to live near the nucleus, and electrons want to complete occupancy to fill their apartments.

Order of Fill

The order of placement of electrons in the orbitals is dependent on the order of their energy. This is called the Aufbau principle. The orbitals of the lowest energy fill first. This order is calculated by measurement, just like the quantum numbers themselves, and is illustrated by the following chart:

Electron configuration

Or by just using the periodic table we can find

Electron configuration

How to Write an Electron Configuration chart-

The symbols used to write the electron configuration start with the shell number (n) followed by the orbital type and finally the superscript shows how many electrons are in the orbital.

Electron configuration

Electron configuration of oxygen-

For example: Looking at the periodic table, you can see that there are 8 electrons in Oxygen. Based on the fill order above, these 8 electrons would fill in 1s, 2s and then 2p in the following order. So the  electron configuration of Oxygen’s would be O 1s22s22p4.

Considering carbon (carbon is the key to life)

The carbon electron structure makes it really great to shape a wide range of molecules needed to sustain life. The configuration looks like


 Notice that there are normally six electrons live in a type “p” orbital, so there is plenty of space available for electrons in carbon atoms to share their orbit with electron of other atom. This makes carbon extremely versatile as it can form stable bonds for different metabolic processes with a wide range of atoms including hydrogen, oxygen, and other essential atoms. Consequently, carbon occurs in a wide range of biochemical compounds, including energy sources, structural building blocks, and essential digestive enzymes. This versatility means a living organism can “recycle” carbon atoms by transferring them easily between different compounds and purposes.

Special Cases

Ion configurations pose a particular case of electron configuration and also show in the first place why these ions are created.

If you need to write an anion’s full electron configuration, you simply add additional electrons and the configuration will simply continue.

For example, we know that when it creates an ion, oxygen often forms2-ions. In its usual configuration, this would add 2 electrons to make the new configuration: O2-1s22s22p6. You must remember with 10 electrons that the electron structure of oxygen is now exactly the same as that of Neon. We talked about the fact that ions evolve because with the gain or loss of electrons they can become more stable to become like noble gasses and now you can really see how they become the same.

Cations ‘ electron arrangements are also made based on the number of electrons, but the way they are designed is slightly different. You should first write their usual electron configuration and then take them from the outermost shell when you extract electrons. Remember that they were not all applied the same way.

Here’s an example of what I mean: Iron has 26 electrons so it would have a standard electron configuration: Fe 1s22s22p63s23p64s23d6

If we make a 3 + ion for Iron, we must first take the electrons from the outermost shell so that it would be the 4s shell NOT the 3d shell: Fe3 + 1s22s22p63s23p63d5 Another note about the electron configurations: a short cut. The overall configuration can be quite long when writing some of the lower table configurations. In these cases, you can abbreviate the specification using the previous noble gas as shown below. The configuration from where the noble gas leaves it must be finished:

Electron configuration


As with any other subject that we have covered up to now, there are also exceptions to the fill order. But these exceptions are easily understood and these are generated based on electron configuration.

There is an exception in how they are filled in the d block, particularly the groups containing chromium and copper.

The real configurations are as follows:

Periodic Properties-

The interesting thing of electronic configuration is their relationship towards periodic table. Periodic table was constructed in such a way that element with same electronic configuration are situated in same group.

Electron configuration

The periodic table shown above illustrates how each element’s arrangement was arranged to make the last filled orbital the same except for the shell. The reason this was achieved is because an element configuration gives its properties to the element and different configurations yield similar properties.

Also Read – What Is Electric Charge

Also Read – What is electricity?

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