Electron Configuration of Chemical Elements

Electron Configuration

The periodic table is a tabular display of the chemical elements organized on the basis of their atomic numbers, electron configurations, and chemical properties. The electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements.

Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. The chemical properties of the atom are determined by the number of protons, in fact, by number and arrangement of electrons. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.

It is the Pauli exclusion principle that requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. The ordering of the electrons in the ground state of multielectron atoms, starts with the lowest energy state (ground state) and moves progressively from there up the energy scale until each of the atom’s electrons has been assigned a unique set of quantum numbers. This fact has key implications for the building up of the periodic table of elements.

electron configuration - blocks - elementsThe first two columns on the left side of the periodic table are where the s subshells are being occupied. Because of this, the first two rows of the periodic table are labeled the s block. Similarly, the p block are the right-most six columns of the periodic table, the d block is the middle 10 columns of the periodic table, while the f block is the 14-column section that is normally depicted as detached from the main body of the periodic table. It could be part of the main body, but then the periodic table would be rather long and cumbersome.

For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. The electron configuration can be visualized as the core electrons, equivalent to the noble gas of the preceding period, and the valence electrons (e.g. [Xe] 6s2 for barium).

Oxidation States

Oxidation states are typically represented by integers which may be positive, zero, or negative. Most elements have more than one possible oxidation state. For example, carbon has nine possible integer oxidation states from −4 to +4.

The current IUPAC Gold Book definition of oxidation state is:

“Oxidation state of an atom is the charge of this atom after ionic approximation of its heteronuclear bonds…”

and the term oxidation number is nearly synonymous. An element that is not combined with any other different elements has an oxidation state of 0. Oxidation state 0 occurs for all elements – it is simply the element in its elemental form. An atom of an element in a compound will have a positive oxidation state if it has had electrons removed. Similarly, adding electrons results in a negative oxidation state. We have also distinguish between the possible and common oxidation states of every element. For example, silicon has nine possible integer oxidation states from −4 to +4, but only -4, 0 and +4 are common oxidation states.

Periodic Table of Elements - electron configuration
1
H

Hydrogen

1s1

2
He

Helium

1s2

3
Li

Lithium

[He] 2s1

4
Be

Beryllium

[He] 2s2

5
B

Boron

[He] 2s2 2p1

6
C

Carbon

[He] 2s2 2p2

7
N

Nitrogen

[He] 2s2 2p3

8
O

Oxygen

[He] 2s2 2p4

9
F

Fluorine

[He] 2s2 2p5

10
Ne

Neon

[He] 2s2 2p6

11
Na

Sodium

[Ne] 3s1

12
Mg

Magnesium

[Ne] 3s2

13
Al

Aluminium

[Ne] 3s2 3p1

14
Si

Silicon

[Ne] 3s2 3p2

15
P

Phosphorus

[Ne] 3s2 3p3

16
S

Sulfur

[Ne] 3s2 3p4

17
Cl

Chlorine

[Ne] 3s2 3p5

18
Ar

Argon

[Ne] 3s2 3p6

19
K

Potassium

[Ar] 4s1

20
Ca

Calcium

[Ar] 4s2

21
Sc

Scandium

[Ar] 3d1 4s2

22
Ti

Titanium

[Ar] 3d2 4s2

23
V

Vanadium

[Ar] 3d3 4s2

24
Cr

Chromium

[Ar] 3d5 4s1

25
Mn

Manganese

[Ar] 3d5 4s2

26
Fe

Iron

[Ar] 3d6 4s2

27
Co

Cobalt

[Ar] 3d7 4s2

28
Ni

Nickel

[Ar] 3d8 4s2

29
Cu

Copper

[Ar] 3d10 4s1

30
Zn

Zinc

[Ar] 3d10 4s2

31
Ga

Gallium

[Ar] 3d10 4s2 4p1

32
Ge

Germanium

[Ar] 3d10 4s2 4p2

33
As

Arsenic

[Ar] 3d10 4s2 4p3

34
Se

Selenium

[Ar] 3d10 4s2 4p4

35
Br

Bromine

[Ar] 3d10 4s2 4p5

36
Kr

Krypton

[Ar] 3d10 4s2 4p6

37
Rb

Rubidium

[Kr] 5s1

38
Sr

Strontium

[Kr] 5s2

39
Y

Yttrium

[Kr] 4d1 5s2

40
Zr

Zirconium

[Kr] 4d2 5s2

41
Nb

Niobium

[Kr] 4d4 5s1

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

47
Ag

Silver

[Kr] 4d10 5s1

48
Cd

Cadmium

[Kr] 4d10 5s2

49
In

Indium

[Kr] 4d10 5s2 5p1

50
Sn

Tin

[Kr] 4d10 5s2 5p2

51
Sb

Antimony

[Kr] 4d10 5s2 5p3

52
Te

Tellurium

[Kr] 4d10 5s2 5p4

53
I

Iodine

[Kr] 4d10 5s2 5p5

54
Xe

Xenon

[Kr] 4d10 5s2 5p6

55
Cs

Caesium

[Xe] 6s1

56
Ba

Barium

[Xe] 6s2

57-71

 

Lanthanoids

 

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

81
Tl

Thallium

[Hg] 6p1

82
Pb

Lead

[Hg] 6p2

83
Bi

Bismuth

[Hg] 6p3

84
Po

Polonium

[Hg] 6p4

85
At

Astatine

[Hg] 6p5

86
Rn

Radon

[Hg] 6p6

87
Fr

Francium

[Rn] 7s1

88
Ra

Radium

[Rn] 7s2

89-103

 

Actinoids

 

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 6d8 7s2

111
Rg

Roentgenium

[Rn] 5f14 6d9 7s2

112
Cn

Copernicium

[Rn] 5f14 6d10 7s2

113
Nh

Nihonium

[Rn] 5f14 6d10 7s2 7p1

114
Fl

Flerovium

[Rn] 5f14 6d10 7s2 7p2

115
Mc

Moscovium

[Rn] 5f14 6d10 7s2 7p3

116
Lv

Livermorium

[Rn] 5f14 6d10 7s2 7p4

117
Ts

Tennessine

[Rn] 5f14 6d10 7s2 7p5

118
Og

Oganesson

[Rn] 5f14 6d10 7s2 7p6

57
La

Lanthanum

[Xe] 5d1 6s2

58
Ce

Cerium

[Xe] 4f1 5d1 6s2

59
Pr

Praseodymium

[Xe] 4f3 6s2

60
Nd

Neodymium

[Xe] 4f4 6s2

61
Pm

Promethium

[Xe] 4f5 6s2

62
Sm

Samarium

[Xe] 4f6 6s2

63
Eu

Europium

[Xe] 4f7 6s2

64
Gd

Gadolinium

[Xe] 4f7 5d1 6s2

65
Tb

Terbium

[Xe] 4f9 6s2

66
Dy

Dysprosium

[Xe] 4f10 6s2

67
Ho

Holmium

[Xe] 4f11 6s2

68
Er

Erbium

[Xe] 4f12 6s2

69
Tm

Thulium

[Xe] 4f13 6s2

70
Yb

Ytterbium

[Xe] 4f14 6s2

71
Lu

Lutetium

[Xe] 4f14 5d1 6s2

89
Ac

Actinium

[Rn] 6d1 7s2

90
Th

Thorium

[Rn] 6d2 7s2

91
Pa

Protactinium

[Rn] 5f2 6d1 7s2

92
U

Uranium

[Rn] 5f3 6d1 7s2

93
Np

Neptunium

[Rn] 5f4 6d1 7s2

94
Pu

Plutonium

[Rn] 5f6 7s2

95
Am

Americium

[Rn] 5f7 7s2

96
Cm

Curium

[Rn] 5f7 6d 7s2

97
Bk

Berkelium

[Rn] 5f9 7s2

98
Cf

Californium

[Rn] 5f10 7s2

99
Es

Einsteinium

[Rn] 5f11 7s2

100
Fm

Fermium

[Rn] 5f12 7s2

101
Md

Mendelevium

[Rn] 5f13 7s2

102
No

Nobelium

[Rn] 5f14 7s2

103
Lr

Lawrencium

[Rn] 5f14 7s2 7p1

Properties of other elements