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Examples of Ionization Energy

The term “ionization energy” is a reference to the quantity of energy necessary to expel an electron from an atom or molecule. As electrons are removed, it becomes more difficult to remove another, as the charge of the atom has changed and the electron is more attracted to stay with the atom. As such, different ionizations of energy can be required under different circumstances and it is important to know how to properly calculate the quantity of energy required.

Understanding Ionization Energy

Ionization energy increases moving from left to right on the periodic table, a table of the elements. The energy decreases moving from top to bottom on the periodic table.

Ionization of energy must be calculated for each ion on the periodic table. As such, to understand ionization of energy, it is helpful to understand the equations that are used in calculating the quantity of energy necessary to expel electrons.

The basic equation for ionization energy is:

X → X+ + e-

The amount of energy necessary changes each time an electron is let go, since it becomes more difficult to remove electrons after one or more has already been removed from the atom or molecule. Therefore, the equation changes.

The different equations are as follows:

  • 1st ionization energy equation

X → X+ + e-

  • 2nd ionization energy equation

X+ → X2+ + e-

  • 3rd ionization energy equation

X2+ → X3+ + e-

Units used to measure ionization are not always the same. Chemists refer to one mole (mol) of a substance when reporting ionization energy. This unit is  kJ/mol or kcal/mol. The unit electron volt (eV) is used by physicists.

Ionization of Energy: Removal of Electrons

Here is a table that shows the ionization energy at each different level of removal of electrons for a variety of elements. (Table from www.shodor.org)

Number

Name

Ionization Energy in Electron Volts (eV)

1

Hydrogen

13.6

2

Helium

24.59

3

Lithium

5.39

4

Beryllium

9.32

5

Boron

8.3

6

Carbon

11.26

7

Nitrogen

14.53

8

Oxygen

13.62

9

Fluorine

17.42

10

Neon

21.56

11

Sodium

5.14

12

Magnesium

7.65

13

Aluminum

5.99

14

Silicon

8.15

15

Phosphorus

10.49

16

Sulfur

10.36

17

Chlorine

12.97

18

Argon

15.76

19

Potassium

4.34

20

Calcium

6.11

21

Scandium

6.56

22

Titanium

6.83

23

Vanadium

6.75

24

Chromium

6.77

25

Manganese

7.43

26

Iron

7.9

27

Cobalt

7.88

28

Nickel

7.64

29

Copper

7.73

30

Zinc

9.39

31

Gallium

6

32

Germanium

7.9

33

Arsenic

9.79

34

Selenium

9.75

35

Bromine

11.81

36

Krypton

14

37

Rubidium

4.18

38

Strontium

5.69

39

Yttrium

6.22

40

Zirconium

6.63

41

Niobium

6.76

42

Molybdenum

7.09

43

Technetium

7.28

44

Ruthenium

7.36

45

Rhodium

7.46

46

Palladium

8.34

47

Silver

7.58

48

Cadmium

8.99

49

Indium

5.79

50

Tin

7.34

51

Antimony

8.61

52

Tellurium

9.01

53

Iodine

10.45

54

Xenon

12.13

55

Cesium

3.89

56

Barium

5.21

57

Lanthanum

5.58

58

Cerium

5.54

59

Praseodymium

5.47

60

Neodymium

5.53

61

Promethium

5.58

62

Samarium

5.64

63

Europium

5.67

64

Gadolinium

6.15

65

Terbium

5.86

66

Dysprosium

5.94

67

Holmium

6.02

68

Erbium

6.11

69

Thulium

6.18

70

Ytterbium

6.25

71

Lutetium

5.43

72

Hafnium

6.83

73

Tantalum

7.55

74

Tungsten

7.86

75

Rhenium

7.83

76

Osmium

8.44

77

Iridium

8.97

78

Platinum

8.96

79

Gold

9.23

80

Mercury

10.44

81

Thallium

6.11

82

Lead

7.42

83

Bismuth

7.29

84

Polonium

8.42

85

Astatine

9.3

86

Radon

10.75

87

Francium

4.07

88

Radium

5.28

89

Actinium

5.17

90

Thorium

6.31

91

Protactinium

5.89

92

Uranium

6.19

93

Neptunium

6.27

94

Plutonium

6.03

95

Americium

5.97

96

Curium

5.99

97

Berkelium

6.2

98

Californium

6.28

99

Einsteinium

6.42

100

Fermium

6.5

101

Mendelevium

6.58

102

Nobelium

6.65

103

Lawrencium

4.9

In eV units, the chart shows the first ionization energy for all elements. To convert to the same measurement as above, multiply by 96.4689.

It is important for those in various scientific fields, including chemistry and physics, to understand the concept of ionization energy and to understand how to use the equations to calculate the ionization energy for each element.

The different equations for different ionizations, therefore, as well as the information on the different ionizations of energy for each element, are very helpful for those who are hoping to better understand how ionization of energy works.

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