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Electron Configuration

Electronic configuration of elements in periodic table

Electronic configuration or general electron configuration or electronic structure of atoms or ions is the arrangement of orbital energy levels for s, p, d, and f-block elements of the periodic table. In chemistry or chemical science, electron holds the key to the chemical world for learning properties and position of elements in the periodic table. The electronic configuration or electron arrangement formula of the periodic table elements is used for better understanding the chemical properties.

Electronic configuration of elements of periodic table and general electron configuration rule for s, p, d and f-block elements

Oxidizing reducing properties, oxidation number, ionization energy, electron affinity, shielding effect, the polarity of chemical bonds, acids bases properties can be explained by the electronic configuration.

A reaction to reach chemical equilibrium is the change of electron configuration of reactant and product atoms. Hence the organic and inorganic chemical reactions are better understood by the electronic configuration of elements.

How to find electronic configuration?

To find the electron configuration formula first we find the order of electronic energy levels of s, p, d, and f orbitals or sub-levels. For example, 3s orbital has lower energy than 3p orbitals which again lower energy than the 3d level.

The modern periodic table classification like s, p, d, and f block elements is based on properties and general electron or electronic configuration of elements.

What are electron energy levels?

Energy levels are fixed distances where electrons are rotating around the nucleus with definite energy. The energy associated with a certain energy level increases with the increase of its distance from the nucleus.

The hydrogen atom contains only one electron in 1s hydrogen energy levels with electronic configuration 1s¹.

But difficult for readers to remember the electron energy levels diagram for many electronic configurations. Therefore, the trivial way but most convenient way to remember these electronic energy levels is given below the diagram.

The different electron orbitals originating from the same electronic energy levels are written in horizontal lines.
Now inclined parallel lines are drawn through the electronic orbitals according to the above picture.
Filling up the different orbitals by the number of electrons will follow these lines configuration. According to above diagram structure, configuration energy levels with electron constructed the following ordering, 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f…

Number of electrons in energy levels

The filling up electronic orbitals with electrons around the nucleus of atoms takes place according to certain rules. The maximum number of electrons in the main energy levels = 2n², where n = principal quantum number.

The maximum number of the electron in sub-shell like s, p, d, and f orbitals = 2(2l + 1). Where l = 0, 1, 2, 3 for s, p, d, f orbitals. Therefore, s, p, d, f energy levels have a maximum of 2, 6, 10, 14 electrons respectively.

Aufbau principle and electron configuration

German scientist Aufbau expresses the building up principle for the electron configuration process in different electronic orbitals of atoms. According to this principle, the electrons are filled up in order of energy.

The orbitals with the lowest energy filled up first while the highest energy orbital filled up in the end. The electron will tend to form maximum spin. Electrons with similar spin are configured first.

What is Hund’s rule?

According to Hund’s rule, electrons are filling in the orbital with maximum spin multiplicity. Spin pairing occurs only when vacant orbitals of similar energy are not available for occupation.

Electronic configuration and periodic table

The electronic configuration formula uses to derive some basic properties like the electromagnetic spectrum, chemical bonding, electric polarization, dipole moment, hydrogen bonding, etc. Modern periodic tables are classified on the basis of chemical behavior and the electronic configuration of elements.

The electron configuration formula of elements must be connected with the periodic table. According to electronic configuration, the periodic table elements are classified into four blocks s, p, d, and f-block elements.

Electronic configuration of s block elements

For s-block elements, the electron enters the ns-orbitals and is progressively filled with atomic number.

Group-1 and 2 belong to s-block elements in the periodic table with general electron configuration ns^1→2, where n = number of electronic shells or the number of periods in which the element is present.

Electronic configuration of group-1 elements

Group-1 or IA in the periodic table contains seven elements like hydrogen, lithium, sodium, potassium, rubidium, cesium, and francium.

The general electronic configuration of valence electron = ns¹, where n = 1 to 7. Due to the presence of one electron in the outer electronic structure, they have very low ionization energy but very high electron affinity.

Atomic number	Symbol	Name	Electronic configuration
1	H	Hydrogen	1s¹
3	Li	Lithium	1s² 2s¹
11	Na	Sodium	[Ne] 3s¹
19	K	Potassium	[Ar] 4s¹
37	Rb	Rubidium	[Kr] 5s¹
55	Cs	Cesium	[Xe] 6s¹
87	Fr	Francium	[Rn] 7s¹

Electronic configuration of group-2 elements

The elements of Group-2 or IIA in the periodic table are beryllium, magnesium, calcium, strontium, barium, and radium. They are also called alkaline earth metals.

The valence shell electronic configuration of group-2 elements or alkaline earth metals is ns², where n = 1 to 6.

Atomic Number	Symbol	Name	Electronic configuration
4	Be	Beryllium	1s² 2s²
12	Mg	Magnesium	[Ne] 3s²
20	Ca	Calcium	[Ar] 4s²
38	Sr	Strontium	[Kr] 5s²
56	Ba	Barium	[Xe] 6s²
88	Ra	Radium	[Rn] 7s²

Electronic configuration of p block elements

The elements in which the p-orbital are progressively filled by electrons are called p-block in the periodic table. Helium whose electronic configuration 1s² but Helium is a member of p-block elements.

p-block contains six groups from group-13 to group-18. The general electronic configuration formula to find the outer electron configuration of the p-block element is ns² np^1→6.

Electronic configuration of group-13 elements

Group-13 or IIIA contains five elements, boron, aluminum, gallium, indium, and thallium. The valence shell electron configuration of group-13 elements is ns² np¹.

Atomic number	Symbol	Name	Electronic configuration
5	B	Boron	1s² 2s² 2p¹
13	Al	Aluminum	[Ne] 3s² 3p¹
31	Ga	Galium	[Ar] 3d¹⁰ 4s² 4p¹
49	In	Indium	[Kr] 4d¹⁰ 5s² 5p¹
81	Tl	Thallium	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
113	Nh	Nihonium	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹

Electronic configuration of group-14 elements

Carbon, silicon, germanium, tin, and lead in the periodic table belong to group-14 or IVA. The general electronic configuration of group-14 elements is ns² np², where n = 2 to 6.

Atomic number	Symbol	Name	Electronic configuration
6	C	Carbon	1s² 2s² 2p²
14	Si	Silicon	[Ne] 3s² 3p²
32	Ge	Germanium	[Ar] 3d¹⁰ 4s² 4p²
50	Sn	Tin	[Kr] 4d¹⁰ 5s² 5p²
82	Pb	Lead	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²
114	Fl	Flerovium	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p²

Electronic configuration of group-15 elements

The five elements of Group-15 or VA are nitrogen, phosphorus, arsenic, antimony, and bismuth. The electronic configuration of group-15 elements is ns² np³, where n = 2 to 6.

Atomic number	Symbol	Name	Electronic configuration
7	N	Nitrogen	1s² 2s² 2p³
15	P	Phosphorus	[Ne] 3s² 3p³
33	As	Arsenic	[Ar] 3d¹⁰ 4s² 4p³
51	Sb	Antimony	[Kr] 4d¹⁰ 5s² 5p³
83	Bi	Bismuth	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³
115	Mc	Moscovium	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p³

Electronic configuration of group-16 elements

Oxygen, sulfur, selenium, tellurium, and polonium in the periodic table belong to group-16 or VIA. The general electronic configuration of group-16 elements is ns² np⁴, where n = 2 to 6.

Atomic number	Symbol	Name	Electronic configuration
8	O	Oxygen	1s² 2s² 2p⁴
16	S	Sulfur	[Ne] 3s² 3p⁴
34	Se	Selenium	[Ar] 3d¹⁰ 4s² 4p⁴
52	Te	Tellurium	[Kr] 4d¹⁰ 5s² 5p⁴
84	Po	Polonium	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴
116	Lv	Livermorium	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁴

Electronic configuration of group-17 elements

Fluorine, chlorine, bromine, iodine, and astatine in the periodic table belong to group-17 or VIIA. The general electronic configuration of group-17 elements is ns² np⁵, where n = 2 to 6.

Atomic number	Symbol	Name	Electronic configuration
9	F	Fluorine	1s² 2s² 2p⁵
17	Cl	Chlorine	[Ne] 3s² 3p⁵
35	Br	Bromine	[Ar] 3d¹⁰ 4s² 4p⁵
53	I	Iodine	[Kr] 4d¹⁰ 5s² 5p⁵
85	As	Astatine	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵
117	Ts	Tennessine	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵

Electronic configuration of noble gases

Neon, argon, krypton, xenon, and radon in the periodic table belong to group-18 or noble gases. The general electronic configuration of noble gases or group-18 elements is ns² np⁶, where n = 1 to 6.

Atomic Number	Symbol	Name	Electronic configuration
2	He	Helium	1s²
10	Ne	Neon	[He] 2s² 2p⁶
18	Ar	Argon	[Ne] 3s² 3p⁶
36	Kr	Krypton	[Ar] 3d¹⁰ 4s² 4p⁶
54	Xe	Xenon	[Kr] 4d¹⁰ 5s² 5p⁶
86	Rn	Radon	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶
118	Os	Oganesson	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶

Electronic configuration of d block elements

The elements in which the electron enters in (n−1)d orbital are called d-block elements. These are placed in the middle of the periodic table, between s and p-block elements due to their chemical behavior like boing point, melting by specific heat, density, ionization energy, bonding, etc.

The general electronic configuration of valence electron of 3d, 4d, 5d, 6d elements represented as ns^0,1,2 (n−1)d^1→10.

These elements are called transition metals or elements. The names, symbols, and valence shell electronic configuration of all the d-block elements or transition metals are given below the picture,

Electronic configuration of 3d-block Elements

The first crystalline solid metal in the 3d-series or first transition series starts with scandium and ends with zinc. When the twenty-first electron goes to the next available higher energy 3d orbital, the five 3d subshells fill with ten electrons.

The general electronic configuration of valence electron of 3d series or first transition series like scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc is [Ar] 4S^1→2 3d^1→10.

Atomic number	Symbol	Name	Electronic configuration
21	Sc	Scandium	[Ar] 4s² 3d¹
22	Ti	Titanium	[Ar] 4s² 3d²
23	V	Vanadium	[Ar] 4s² 3d³
24	Cr	Chromium	[Ar] 4s¹ 3d⁵
25	Mn	Manganese	[Ar] 4s² 3d⁵
26	Fe	Iron	[Ar] 4s² 3d⁶
27	Co	Cobalt	[Ar] 4s² 3d⁷
28	Ni	Nickel	[Ar] 4s² 3d⁸
29	Cu	Copper	[Ar] 4s¹ 3d¹⁰
30	Zn	Zinc	[Ar] 4s¹ 3d¹⁰

4d-block elements

Atomic number	Symbol	Name	Electronic configuration
39	Y	Yttrium	[Kr] 4d¹ 5s²
40	Zr	Zirconium	[Kr] 4d² 5s²
41	Nb	Niobium	[Kr] 4d³ 5s²
42	Mo	Molybdenum	[Kr] 4d⁵ 5s¹
43	Tc	Technetium	[Kr] 4d⁵ 5s²
44	Ru	Ruthenium	[Kr] 4d⁷ 5s¹
45	Rh	Rhodium	[Kr] 4d⁸ 5s¹
46	Pd	Palladium	[Kr] 4d¹⁰ 5s⁰
47	Ag	Silver	[Kr] 4d¹⁰ 5s¹
48	Cd	Cadmium	[Kr] 4d¹⁰ 5s²

5d-block elements

Atomic number	Symbol	Name	Electronic configuration
57	La	Lanthanum	[Xe] 5d¹ 6s²
72	Hf	Hafnium	[Xe] 4f¹⁴ 5d² 6s²
73	Ta	Tantalum	[Xe] 4f¹⁴ 5d³ 6s²
74	W	Tungsten	[Xe] 4f¹⁴ 5d⁴ 6s²
75	Re	Rhenium	[Xe] 4f¹⁴ 5d⁵ 6s²
76	Os	Osmium	[Xe] 4f¹⁴ 5d⁶ 6s²
77	Ir	Iridium	[Xe] 4f¹⁴ 5d⁷ 6s²
78	Pt	Platinum	[Xe] 4f¹⁴ 5d⁹ 6s¹
79	Au	Gold	[Xe] 4f¹⁴ 5d¹⁰ 6s¹
80	Hg	Mercury	[Xe] 4f¹⁴ 5d¹⁰ 6s²

6d-block elements

Atomic number	Symbol	Name	Electronic configuration
89	Ac	Actinium	[Rn] 6d¹ 7s²
104	Rf	Rutherfordium	[Rn] 5f¹⁴ 6d² 7s²
105	Db	Dubnium	[Rn] 5f¹⁴ 6d³ 7s²
106	Sg	Seaborgium	[Rn] 5f¹⁴ 6d⁴ 7s²
107	Bh	Bohrium	[Rn] 5f¹⁴ 6d⁵ 7s²
108	Hs	Hassium	[Rn] 5f¹⁴ 6d⁶ 7s²
109	Mt	Meitnerium	[Rn] 5f¹⁴ 6d⁷ 7s²
110	Ds	Darmstadtium	[Rn] 5f¹⁴ 6d⁹ 7s¹
111	Rg	Roentgenium	[Rn] 5f¹⁴ 6d¹⁰ 7s¹
112	Cn	Copernicium	[Rn] 5f¹⁴ 6d¹⁰ 7s²

Exceptional electron configuration

Chromium, and copper, the 3d elements of our environment reveal their general form of electron or electronic configuration trends in the periodic table. The general electronic configuration valence electron of chromium and copper are [Ar]4s² 3d⁴ and [Ar] 4s² 3d⁹.

In the periodic table elements, the half-filled and filled orbitals electron configuration formula is relatively more stable than the partially filled orbitals. Thus 3d orbital of chromium and copper recording to form new electronic configuration like [Ar]4s¹ 3d⁵ and [Ar] 4s¹ 3d¹⁰ to gain extra chemical stability by exchange energy.