Introduction:
Ionization potential is an important concept in chemistry and physics, as it helps to explain many properties of atoms and molecules, including their reactivity, chemical bonding, and spectroscopic behavior.
The ionization potential of an atom or molecule depends on the number of electrons it has and its atomic or molecular structure. Atoms and molecules with more electrons or tighter electron bonding require more energy to remove an electron and thus have higher ionization potentials.
Ionization Potential:
Ionization potential, also known as ionization energy, is the amount of energy required to remove an electron from a neutral atom or molecule in its ground state.
Gaseous neutral atom + ionization energy -> Gaseous Ion + Gaseous electron removed Infinite distance away from nucleus
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| Ionization Potential OR Ionization Energy |
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| Ionization Potential OR Ionization Energy ( First, Second and Third ionization energy ) |
Units:
It is expressed in kJ per mole.
First Ionization Potential:
The first ionization potential (IP1) is the minimum amount of energy required to remove the outermost or valence electron from a neutral atom or molecule in the gaseous state.
The first ionization potential generally increases across a period in the periodic table, as the effective nuclear charge (the positive charge felt by the valence electrons) increases. This means that the valence electrons are more strongly attracted to the nucleus and require more energy to be removed. Conversely, the first ionization potential generally decreases down a group in the periodic table, as the distance between the valence electrons and the nucleus increases, making the valence electrons easier to remove.
M (g) + First Ionization Energy ( I1 ) -> M⁺(g) + e-(g)
A magnesium atom has got twelve electrons outside the nucleus. To remove one electron from a neutral gaseous atom to convert it into a unipositive ion, the required energy is equal to 738 kJ per mole.
Mg (g) + 738 kJ per mole -> Mg⁺ (g) + e-(g)
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First Ionization Energy |
Second Ionization Potential:
The energy required to remove one electron from a unipositive gaseous ion to from one bipositive gaseous ion is known as the second ionization potential.
For example, to remove one more electron from the unipositive ion of magnesium to convert it into a bipositive ion, the energy needed is equal to 1450 kJ per mole. Thus second ionization potential of magnesium is 1450 kJ per mole.
M⁺(g) + Second Ionization -> M⁺⁺ (g) + e-(g)
For Magnesium
Mg⁺ (g) + 1450kJ per mole -> Mg⁺⁺ (g) + e-(g)
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| Second ionization energy |
Third Ionization Potential:
The energy required to remove the third electron from the gaseous bipositive ion from one tripositive ion is known as the third ionization potential.
In the same manner fourth, fifth, or six, etc, ionization potential can be defined.
M⁺⁺ (g) + Third Ionization Energy -> M⁺⁺⁺ (g) + e-(g)
For magnesium third ionization potential is very high 7730 kJ per mole in comparison with I1 & I2.
Mg⁺⁺ (g) + 7730 kJ per mole -> Mg⁺⁺⁺ (g) + e-(g)
The first ionization Potential I1 is lesser than the second ionization potential and third ionization potential I3 is greater than these two. It is because after the removal of each electron, the remaining electrons are more strongly attracted by the nucleus. Thus more energy is needed to take out an electron. In the case of magnesium, the Third ionization is very high because the third electron is to be removed from a complete shell.