Basic chemistry

Electronic configuration and periodic table?

Electronic configuration

Electronic configuration in periodic table ?

Electronic configuration :

electronic configuration
calculation of electronic configuration

The electronic configuration in periodic table of an atom is the numerical distribution of electrons in its energy layers.

The energy layers are the different regions around the atom where the electrons are statistically most likely to be.

The electronic configuration makes it possible to quickly and simply inform on the number of layers of energies that an atom possesses, as well as on the number of electrons that populate each layer of this atom.

Once you understand the basics behind the term “electronic setup,” you’ll be able to write your own setups and tackle your chemistry exams with confidence.


Assign the number of electrons using the periodic table of elements

  1. 1

    Find the atomic number of your atom. Each atom has a specific number of electrons associated with it. Locate the chemical symbol of your atom in the periodic table.
  2. The atomic number is a positive integer beginning with 1 (for hydrogen) and increasing by 1 in 1 for each subsequent atom. The atomic number of an atom is the number of protons that this atom contains – and therefore, the number of electrons in a non-charged atom.
  3. Determine the charge of your atom. Uncharged atoms will have exactly the same number of electrons as indicated in the periodic table. On the other hand, the charged atoms will have a higher or lower number of electrons depending on their charge. If you are working on a charged atom, add or subtract the electrons as follows: add one electron for each negative charge and subtract one electron for each positive charge.

    • For example, a sodium atom with a charge of -1 will have an additional electron in addition to its initial atomic number of 11. Therefore, the sodium atom in question will have a total of 12 electrons.
  4. 3

    Memorize the basic list of electronic sub-layers. As an atom gains electrons, they fill different electronic sub-layers in a specific order. Once filled, each electronic sublayer comprises a regular number of electrons. The different types of electronic sub-layers are:

    • The s -type sublayer (number followed by an “s” in the electronic configuration) contains a single quantum box. According to the Pauli exclusion principle , a quantum box can contain at most 2 electrons, so each s-type sublayer can contain 2 electrons.
    • The p-type sublayer contains 3 quantum boxes, and can therefore contain a total of 6 electrons.
    • The d-type sublayer contains 5 quantum boxes, and can therefore contain a total of 10 electrons.
    • The f-type sublayer contains 7 quantum boxes, and can therefore contain a total of 14 electrons.
  5. 4

    Understand the notation used for the electronic configuration. The electronic configurations are written to clearly represent the number of electrons of an atom as well as the number of electrons present on each sublayer of this atom. The sub-layers are written in a precise sequence, with the number of atoms present on each electronic sub-layer written by exposing on the right of the name of this one. The final electronic configuration consists of a single line comprising the electronic sub-layers followed by superscript numbers.

    • For example, here is a simple electronic configuration: 1s 2 2s 2 2p 6 . This configuration means that there are two electrons in the 1s sublayer, two electrons in the 2s sublayer, and six electrons in the 2p sublayer. 2 + 2 + 6 = 10 electrons in total. This electronic configuration is that of the unfilled neon atom (the atomic number of neon is 10).
  6. 5

    Memorize the order of the electronic sub-layers. Note that sub-layers are numbered by electron layers, but ordered by energy level. For example, an undercoat layer 4s 2 filled has a lower energy (is potentially more stable) a sub-layer 3d 10 partially filled; so the 4s sub-layer appears before in the list. Once you know the order of the sub-layers, you can fill them simply according to the number of electrons carried by the atom. The order of filling of the sub-layers is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p , 8s .

    • The electronic configuration of an atom with all the underlays completely filled in is written as follows: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 6 8s 2 .
    • Note that the previous list would be the electronic configuration of the Uuo (symbol of ununoctium), atomic number 118, the highest of the Periodic Table of Elements – implying that this electronic configuration includes all known electronic sublayers today for a zero charge atom.
  7. 6

    Fill the sub-layers according to the number of electrons carried by your atom. For example, to write the electronic configuration of an uncharged calcium atom, you will first have to look for its atomic number in the periodic table of elements. Since its atomic number is 20, you will have to write the electronic configuration of an atom comprising 20 electrons in the order given in the previous paragraph.

    • Fill the electronic sub-layers in the order given above, until you have reached 20 electrons. The sub-layers 1s and 2s each carry 2 electrons, the 2p at the gate 6, the 3s at the gate 2, the 3p at the gate 6, and the 4s at the gate 2 (2 + 2 + 6 + 2 + 6 + 2 = 20 ). The electronic configuration of calcium is therefore: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 .
    • Note: The energy level climbs from one layer to another. For example, when you go to the 4th level of energy, you go to the underlay 4s, then you go back to the 3d. After the 4th level of energy, you will go to the 5th and follow the order again. This only happens from the 3rd level of energy.
  8. 7

    Use the periodic table as a visual shortcut. You may have already noticed that the shape of the periodic table corresponds to the order of the electronic sub-layers of the periodic configurations of the elements. For example, the elements in the second column from the left always end in “s 2  “, while the rightmost atoms in the middle part all end in “d 10 “, and so on. Use the periodic table to help you write the configurations – the order in which you add the electrons to the sub-layers corresponds to the position of the element in question in the table. More precisely :

    • The electronic configuration of the atoms in the leftmost two columns ends with the underlayer s, while that of the atoms on the right side of the array ends with the underlayer p. The configuration of the atoms placed at the center ends with the underlayer d, and that of the atoms at the bottom of the array ends with the underlayer f.
    • For example, if you are looking for the electronic configuration of chlorine, you must say: “This atom is in the third line (or” period “) of the periodic table. It is also in the 5th column of the part of the table so the underlayments end in p. So, its electronic configuration will end with 3p 5 .
    • Attention: the areas of the table corresponding to the sub-layers d and f correspond to energy levels different from those of the periods in which they are. For example, the first line of the block corresponding to the sub-layer d correspond to the third layer of energy although they are in the period 4, while the first line of the orbital f corresponds to the underlayer 4f even if it is in period 6.
  9. 8

    Learn shortcuts to write long electronic configurations. The atoms in the rightmost column of the periodic table are called rare gases . These elements are chemically very stable. To write faster electronic configurations, simply write the chemical symbol for the nearest noble gas that has fewer electrons than your atom in square brackets, and then continue searching for the electronic configuration for the remaining underlayments. Here is an example :

    • To understand this concept, it may be useful to take an example of an electronic configuration. Let’s write the zinc configuration (atomic number = 30) using the rare gases. The complete electronic configuration of zinc is as follows: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 However, you will have noticed that 1s 2 2s 2 2p 6 3s 2 3p 6 is the configuration of argon, a rare gas. Replace this portion of the electronic zinc configuration with the argon chemical symbol in square brackets ([Ar]).
    • Therefore, the electronic configuration of zinc can be written [Ar] 4s 2 3d 10.
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