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Electronic Configuration

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The distribution of electrons in various shell, sub shells and orbitals in an atom of an element is known as its complete electronic configuration. The distribution of electrons in various sub-shells or orbitals of the valence shell of an atom is called valence shell configuration.

The electronic configuration of an atom is written in terms of nlx notation, when l=0 (s-sub shell), 1 (p-sub shell), 2 (d-sub shell) and 3 (f-sub shell). In this notation the superscript x, written at the top if l indicates the number of electrons present in the sub shell, given by l, while n written to the left of l indicates the number of shell to which the sub shell denoted by l belongs.


Electronic configuration is a means of stating which kinds of orbitals contain electrons and the numbers of electrons and the numbers of electrons in each kind of orbital of an atom. It is expressed by the number and letter representing each kind of orbital and superscript numbers telling how many electrons are in each sub level.

Electron Configuration Definition

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What is Electronic Configuration?

Electronic configuration has to do with the order in which electrons fill energy levels in the atoms of the elements of the atomic periodic table.

An electronic configuration of an organic molecule is defined as a listing of the MOs that are occupied with electrons in the configuration. Thus an electron configuration tells us how the electrons are distributed among the available orbitals and also provides a description of the electronic distribution of a molecule from the knowledge of the spatial distribution of the orbitals.

Valence Electron Configuration

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The valence electron configuration of an atom essentially defines its personality. This personality includes the atoms size its appetite for electrons and its willingness to associate with other atoms in chemical bonding.

One of the justifications for grouping elements as we do in the periodic table have the same number of valence electrons in the same shapes of orbitals. In general the number of valence electrons in the same shapes of orbitals.

In general the number of valence electrons of an atom equals its group number. In the old styles of numbering periodic tables the number of valence electrons equals the group number as long as the groups in a given part of the periodic table are consecutively numbered. The groups of f-block elements are not numbered at all in a conventional periodic table, so we must count over from La and Ac as "3" or Ce and Th as "4". Lu and Lr should be numbered as having three valence electrons.

Ground State Electron Configuration

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The ground state configuration is defined as the configuration for which the orbitals that are occupied produce the state of lowest energy. All other electronic configurations correspond to electronically excited states.

Each element has a distinctive configuration of electrons in orbitals its electron configuration. The lowest energy state an atom can have is described as its ground state. The electron configuration of the ground state of atoms of any element is determined by applying the rules.

The ground state electron configuration for first 10 elements are listed below.

S.No
Element
Atomic number
Electronic configuration
Number of electrons in each orbital
1
H 1s1 1
2
2
2
2
2
2
2
2
2
1
2
2
2
2
2
2
2
1
1
1
2
2
2
1
1
1
2
2
1
1
1
2
2
He
2
1s2
3
Li
3
1s22s1
4
Be 4
1s22s2
5
B
5
1s22s22p1
6
6
1s22s22p2 
7
N
7
1s22s22p3
8
8
1s22s22p4 
9
9
1s22s22p5 
10
Ne 10
1s22s22p6 

The Excited State Electron Configuration are that they must contain the same total number of electrons as the ground state, and no energy level, or sub level can have more than its maximum number of electrons.

Periodic Table with Electron Configuration

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There is a close relation between electronic configuration and long form of periodic table.
  1. Each successive period in periodic table is concerned with filling of next higher principle energy level.
  2. It is observed that the number of elements in each period is twice the number of atomic orbitals being filled.
  3. The sixth period (n=6) contains 32 elements and successive electrons enter 6s, 4f, 5d and 6p orbitals in that order.
  4. Elements in the same vertical column or group have similar electronic configuration have the same number of electrons in outermost orbitals and similar properties.
  5. The elements placed in the same group or family constitute a family of elements having similar properties.

The periodic table based on the blocks in the periodic table is given below.

Periodic Table with Electron Configuration

Electron Configuration Diagram

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The depiction of electron configuration is the orbital box diagram , but the most frequency method is spdf method. The electron configuration diagrams is shown below.

Electron Configuration Diagram
Diagram of Electron Configuration

Electron Configuration Rules

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Electrons occupy orbitals in a predictable pattern according to these three rules.
  1. Orbitals of lowest energy fill first. (the Aufbau principle)
  2. A maximum of two electrons (of opposite spin) may occupy a single orbital (the Pauli exclusion principle)
  3. When more than one orbital of the same energy is empty each of these orbitals will first acquire one electron before any orbital acquires the second electron (Hund's rule) 

Electron configuration Chart

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Electron configuration is the shape of the electrons around the atom, that is which energy level and what kind of orbital it is in. The electron configuration list is given below.

Atomic Number
Name of element Symbol
Group Electron
Configuration
Symbol, group/series/block and Comments
1
Hydrogen H
1 1s1
2 Helium
He
18 1s2 Group 0/18 Noble Gas,
3 Lithium
Li
1 [He] 2s1 s-block, Group 1 Alkali Metal,
4 Beryllium
Be 2 [He] 2s2 s-block, Group 2 Alkaline Earth Metal,
5 Boron B
13 [He] 2s2 2p1 p-block, Group 3/13
6 Carbon C
14 [He] 2s2 2p2 p-block, Gp4/14,
7 Nitrogen
N
15 [He] 2s2 2p3 p-block, Gp5/15,
8 Oxygen O
16 [He] 2s2 2p4 p-block, Gp6/16,
9 Fluorine F
17 [He] 2s2 2p5 p-block, G p7/17 Halogen,
10 Neon Ne
18 [He] 2s2 2p6 p-block, Gp 0/18 Noble Gas,
11 Sodium Na
1 [Ne] 3s1 Gp1 Alkali Metal,
12 Magnesium
Mg
2 [Ne] 3s2 s-block, Gp2 Alkaline Earth Metal,
13 Aluminum
Al
13 [Ne] 3s2 3p1 p-block, Gp3/13,
14 Silicon
Si
14 [Ne] 3s2 3p2 p-block, Gp4/14,
15 Phosphorus
P
15 [Ne] 3s2 3p3 p-block, Gp5/15,
16 Sulfur
S
16 [Ne] 3s2 3p4 p-block, Gp6/16,
17 Chlorine
Cl
17 [Ne] 3s2 3p5 p-block, Gp7/17 Halogen,
18 Argon
Ar
18 [Ne] 3s2 3p6 p-block, Gp 0/18 Noble Gas,
19 Potassium
K
1 [Ar] 4s1 s-block, Gp1 Alkali Metal,
20 Calcium
Ca
2 [Ar] 4s2 s-block, Gp2 Alkaline Earth Metal,
21 Scandium
Sc
3 [Ar] 3d1 4s2 3d block, not true
Transition Metal
22 Titanium
Ti
4 [Ar] 3d2 4s2 3d block, a true Transition Metal
23 Vanadium
V 5 [Ar] 3d3 4s2 3d block, a true Transition Metal
24 Chromium Cr
6 [Ar] 3d5 4s1 3d block, a true Transition Metal
25 Manganese Mn
7 [Ar] 3d5 4s2 3d block, a true Transition Metal
26 Iron
Fe
8 [Ar] 3d6 4s2 3d block, a true Transition Metal
27 Cobalt
Co 9 [Ar] 3d7 4s2 3d block, a true Transition Metal
28 Nickel
Ni 10 [Ar] 3d8 4s2 3d block, a true Transition Metal
29 Copper
Cu 11 [Ar] 3d10 4s1 3d block, a true Transition Metal
30 Zinc
Zn 12 [Ar] 3d10 4s2 3d block, not true Transition Metal
31 Gallium
Ga 13 [Ar] 3d10 4s2 4p1 p-block, Gp3/13,
32 Germanium
Ge 14 [Ar] 3d10 4s2 4p2 p-block, Gp4/14,
33 Arsenic
As 15 [Ar] 3d10 4s2 4p3 p-block, Gp5/15,
34 Selenium
Se 16 [Ar] 3d10 4s2 4p4 p-block, Gp6/16,
35 Bromine
Br 17 [Ar] 3d10 4s2 4p5 p-block, Gp7/17 Halogen,
36 Krypton Kr 18 [Ar] 3d10 4s2 4p6 p-block, Gp 0/18 Noble Gas,
37 Rubidium Rb 1 [Kr] 5s1 s-block, Gp1 Alkali Metal,
38 Strontium Sr 2 [Kr] 5s2 s-block, Gp2 Alkaline Earth Metal,
39 Yttrium Y 3 [Kr] 4d1 5s2 4d block, not true Transition Metal
40 Zirconium
Zr 4 [Kr] 4d2 5s2 4d block, a true Transition Metal
41 Niobium Nb 5 [Kr] 4d4 5s1 4d block, a true Transition Metal
42 Molybdenum Mo 6 [Kr] 4d5 5s1 4d block, a true Transition Metal
43 Technetium Tc 7 [Kr] 4d5 5s2 4d block, a true Transition Metal
44 Ruthenium Ru 8 [Kr] 4d7 5s1 4d block, a true Transition Metal
45 Rhodium Rh 9 [Kr] 4d8 5s1 4d block, a true Transition Metal
46 Palladium Pd 10 [Kr] 4d10 4d block, a true Transition Metal
47 Silver Ag 11 [Kr] 4d10 5s1 4d block, a true Transition Metal
48 Cadmium Cd
12 [Kr] 4d10 5s2 4d block, a true Transition Metal
49 Indium In 13 [Kr] 4d10 5s2 5p1 p-block, Gp3/13,
50 Tin Sn 14 [Kr] 4d10 5s2 5p2 p-block, Gp4/14,
51 Antimony Sb 15 [Kr] 4d10 5s2 5p3 p-block, Gp5/14,
52 Tellurium Te 16 [Kr] 4d10 5s2 5p4 p-block, Gp6/16,
53 Iodine I 17 [Kr] 4d10 5s2 5p5 p-block, Gp7/17 Halogen,
54 Xenon Xe 18 [Kr] 4d10 5s2 5p6 p-block, Gp 0/18 Noble Gas,
55 Cesium Cs 1 [Xe] 6s1 s-block, Gp1 Alkali Metal,
56 Barium Ba 2 [Xe] 6s2 s-block, Gp2 Alkaline Earth Metal,
57 Lanthanum La 3 [Xe] 5d1 6s2 Start of 5d-bock and Lanthanide Series
58 Cerium Ce 101 [Xe] 4f1 5d1 6s2 1st of f-block in the Lanthanides Metals
59 Praseodymium Pr
101 [Xe] 4f3 6s2 f-block in the Lanthanides Metals
60 Neodymium Nd
101 [Xe] 4f4 6s2 f-block in the Lanthanides Metals
61 Promethium Pm 101 [Xe] 4f5 6s2 f-block in the Lanthanides Metals
62 Samarium Sm 101 [Xe] 4f6 6s2 f-block in the Lanthanides Metals
63 Europium Eu 101 [Xe] 4f7 6s2 f-block in the Lanthanides Metals
64 Gadolinium Gd 101 [Xe] 4f7 5d1 6s2 f-block in the Lanthanides Metals
65 Terbium Tb 101 [Xe] 4f9 6s2 f-block in the Lanthanides Metals
66 Dysprosium Dy 101 [Xe] 4f10 6s2 f-block in the Lanthanides Metals
67 Holmium Ho 101 [Xe] 4f11 6s2 f-block in the Lanthanides Metals
68 Erbium Er 101 [Xe] 4f12 6s2 f-block in the Lanthanides Metals
69 Thulium Tm
101 [Xe] 4f13 6s2 f-block in the Lanthanides Metals
70 Ytterbium Yb
101 [Xe] 4f14 6s2 f-block in the Lanthanides Metals
71 Lutetium Lu
101 [Xe] 4f14 5d1 6s2 f-block in the Lanthanides Metals
72 Hafnium Hf
4 [Xe] 4f14 5d2 6s2 d-block element
73 Tantalum Ta 5 [Xe] 4f14 5d3 6s2 d-block element
74 Tungsten W 6 [Xe] 4f14 5d4 6s2 d-block element
75 Rhenium Re 7 [Xe] 4f14 5d5 6s2 d-block element
76 Osmium Os 8 [Xe] 4f14 5d6 6s2 d-block element
77 Iridium Ir 9 [Xe] 4f14 5d7 6s2 d-block element
78 Platinum Pt 10 [Xe] 4f14 5d9 6s1 d-block element
79 Gold Au 11 [Xe] 4f14 5d10 6s1 d-block element
80 Mercury Hg 12 [Xe] 4f14 5d10 6s2 d-block element
81 Thallium TI 13 [Xe]4f14 5d10 6s2 6p1 p-block element
82 Lead Pb 14 [Xe]4f14 5d10 6s2 6p2 p-block element
83 Bismuth Bi 15 [Xe]4f14 5d10 6s2 6p3 p-block element
84 Polonium Po 16 [Xe]4f14 5d10 6s2 6p4 p-block element
85 Astatine At 17 [Xe]4f14 5d10 6s2 6p5 p-block element
86 Radon Rn 18 [Xe]4f14 5d10 6s2 6p6 p-block element
87 Francium Fr 1 [Rn] 7s1 s-block radioactive element from 1st group
88 Radium Ra 2 [Rn] 7s2 s-block radioactive element from 2nd group
89 Actinium Ac 3 [Rn] 6d1 7s2 d-block element , 1st element of actinide
90 Thorium Th 102 [Rn] 6d2 7s2 f-block element , actinide
91 Protactinium Pa 102 [Rn] 5f2 6d1 7s2 f-block element , actinide
92 Uranium U 102 [Rn] 5f3 6d1 7s2 f-block element , actinide
93 Neptunium Np 102 [Rn] 5f4 6d1 7s2 f-block element , actinide
94 Plutonium Pu 102 [Rn] 5f6 7s2 f-block element , actinide
95 Americium Am 102 [Rn] 5f7 7s2 f-block element , actinide
96 Curium Cm 102 [Rn] 5f7 6d1 7s2 f-block element , actinides
97 Berkelium Bk 102 [Rn] 5f97s2 f-block element , actinides
98 Californium Cf 102 [Rn] 5f107s2 f-block element , actinides
99 Einsteinium Es 102 [Rn] 5f117s2 f-block element , actinides
100 Fermium Fm 102 [Rn] 5f127s2 f-block element , actinides
101 Mendelevium Md 102 [Rn] 5f137s2 f-block element , actinides
102 Nobelium No 102 [Rn] 5f147s2 f-block element , actinides
103 Lawrencium Lr 102 [Rn] 5f146d17s2 f-block element , actinides
104 Rutherfordium Rf 4 [Rn] 5f146d27s2 Artificial radioactive element and the first transactinide element.
105 Dubnium Db 5 [Rn] 5f146d37s2 Artificial radioactive element
106 Seaborgium Sg 6 [Rn] 5f146d47s2 Artificial radioactive element that does not occur in nature
107 Bohrium Bh 7 [Rn] 5f146d57s2 Radioactive element
108 Hassium Hs 8 [Rn] 5f146d67s2 Radioactive element
109 Meitnerium Mt 9 [Rn]5f146d77s2 Radioactive element

The arrangements of metals in the order of reactivity are called reactivity series. In other words a series of elements ranked in order of reactivity also known as reactivity series. It also measures the readiness of the metals to give up electrons to form positive ions.
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The Schrodinger equation can be solved approximately for atoms with two or more electrons. There are many solutions for the wave functions $\psi$, each associated with a set of numbers called quantum numbers. It is required to completely describe a specific electron in a multi-electron atom.
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Hyperconjugation involves binding n atoms to a central atom using fewer than n electron pairs around the central atom. Hyperconjugation is an interaction between an empty p orbital with the adjacent C-H sigma bond. Hyperconjugation is referred to as no bond resonance. It is also defined as the delocalization involving sigma bond.
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Aufbau principle is used to determine the electron configuration of a particular atom, it is also called as "building up" principle. Electrons are placed into orbitals from lowest energy orbital to highest energy orbital. Aufbau is a German word which means building up or construction. This is the reason that this principle is also known as building up principle or the construction principle.
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To predict the electronic configuration the location of the particular element in the periodic table must be known. To aid this valence electrons are defined in which valence electrons with the highest principle quantum number in an atom and any electrons as unfilled sub shell from a lower shell. The orbitals in which the valence electrons reside are called the valence orbitals.
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