Periodic Table and Element Energy Diagram

If we analyze the electronic distribution of a given atom in the energy diagram (or diagram of Pauling) it is possible to 'predict' two questions regarding the location of the element of this atom in the Table Periodical: the period and the family.

Let us first consider the period:

For example, consider the case of four elements from different periods:

·Be (Z = 4): A geometric order of the electronic distribution of beryllium is: 1s² / 2s².

See that 2 levels have been filled, so the beryllium is from the 2º time course.

·Na (Z = 11): The geometric order of the electronic distribution of sodium is: 1s² / 2s² 2p⁶ / 3s¹.

In this case, 3 levels were filled, so the sodium is from the 3º time course.

·As (Z = 33): The geometric order of the electronic distribution of arsenic is: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 3d¹⁰ / 4s²4P³.

4 levels were filled, so the arsenic is from the 4º time course.

·I (Z = 53): The geometric order of the electronic distribution of iodine is: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 3d¹⁰ / 4s² 4p⁶ 4d¹⁰ / 5s²5P⁵.

5 levels were filled, so the iodine is from the 5º time course.

Now let's consider how we can discover the element family:

See how this happens in each of the element groups mentioned above:

·Representative Elements:

These elements are those that belong to the families: 1, 2, 13, 14, 15, 16, 17 and 18. They are also called typical or characteristic elements and in tables not yet updated they correspond to the elements that are in columns A (IA, IIA, IIIA, IVA, VA, VIA, VIIA, VIII A).

Whenever the most energetic electron is in an s or p sublevel, it will be a representative element. Furthermore, the sum of the electrons that have been filled in at the outermost level shows us what their respective family is.

See how this happens:

·Family 1: All have 1 electron in the last energy level.

Examples:

₁H: 1s¹ → Despite not being an alkali metal, hydrogen appears in the table in family 1 because it has 1 electron in its last and only shell.

₃I read: 1s² / 2s¹

₁₁In: 1s² / 2s² 2p⁶ / 3s¹

₁₉K: 1s² / 2s² 2p⁶ / 3s² 3p⁶  / 4s¹

₃₇Rb: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 3d¹⁰ / 4s² 4p⁶ / 5s¹

Do not stop now... There's more after the advertising ;)

₅₅Cs: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 3d¹⁰ / 4s² 4p⁶ 4d¹⁰ / 5s² 5p⁶ / 6s¹

₈₇Fr: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 3d¹⁰ / 4s² 4p⁶ 4d¹⁰ 4f¹⁴ / 5s² 5p⁶ 5d¹⁰ / 6s² 6p⁶  / 7s¹

Thus, we can conclude that the electronic configuration of the elements of this group ends with us¹ (n = 1 to 7).

This helps us to see that there is then a generalization to other groups or families:

·Family 2: All have 2 electrons in the last level and the electron configuration ends in us².

·Family 13: All have 3 electrons in the last level and the electron configuration ends in us² np¹.

·Family 14: All have 4 electrons in the last level and the electron configuration ends in us² np².

·Family 15: All have 5 electrons in the last level and the electron configuration ends in us² np³.

·Family 16: All have 6 electrons in the last level and the electron configuration ends in us² np⁴.

·Family 17: All have 7 electrons in the last level and the electron configuration ends in us² np⁵.

•  External transition elements:

The transition elements are those that are in families from 3 to 12, and the external transition elements are those that are exposed (external). In the old tables, transition elements occupy columns B.

They have the electron more energetic on a sublevel d incomplete. Your electronic configuration ends in us² (n-1)d ^{(1 to 8)}.

See two examples, whose settings are now in energy order:

₂₈Ni: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²3d⁸

₃₉Y: 1s² 2s² 2p⁶ 3s² 3p⁶  4s² 3d¹⁰ 4p⁶ 5s²4d¹

•  Internal transition elements:

These are elements that occupy group 3 of the Periodic Table, but remain internal and, to see them, we pull a line repeating periods 6 and 7 below the table. Period 6 is called the lanthanide series, and period 7 is the actinide series.

Internal transition elements have the most energetic electron of the atom in the ground state in a incomplete sublevel f. Your electronic configuration ends in us² (n - 2)f ^{(1 to 13)}.

Example with electronic configuration in power order:

₅₇La: 1s² / 2s² 2p⁶ / 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶6s² 4f¹.

By Jennifer Fogaça
Graduated in Chemistry

Would you like to reference this text in a school or academic work? Look:

FOGAÇA, Jennifer Rocha Vargas. "Periodic Table and Element Energy Diagram"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/tabela-periodica-diagrama-energia-dos-elementos.htm. Accessed on June 27, 2021.