Why do inert gases have the highest ionization energy in the periodic table?Explain briefly.

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Wilson2014 | eNotes Employee

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Inert gases, also known as "noble gases," are the group 18 chemical elements on the periodic table. They are highly unreactive because its outermost atomic orbital has been filled to its maximum capacity of 8 electrons. Electrons in an atom's outermost atomic orbital are called, "valence electrons." Having 8 valence electrons is the most stable energy state (meaning lowest in energy) that an atom in its respective period can exist in. This explains why it is unlikely that inert gases will participate in chemical reactions because this will involve losing, gaining, or sharing a valence electron. If this were to happen, they will deviate from their lowest energy state of 8 valence electrons and move to a state of higher energy since they no longer have that full octet in their outermost atomic orbital. 

Therefore, the highest ionization energy of these inert gases in their respective periods on the periodic table can be explained by these concepts of highest stability and lowest energy when the atom's outermost atomic orbital is filled to capacity with 8 valence electrons. Ionization energy is the energy required to remove a valence electron from an atom. Since inert gases are in their most stable form, it is more unfavorable to remove their valence electrons than those of any other atom in the same period. As a result, more energy (ionization energy) is required to "pull" a valence electron away from inert gases. The ionization energy is the energy that is given to the atom so that it may exist in a higher energy state without its very favorable and stable full octet. 

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jerichorayel | College Teacher | (Level 2) Senior Educator

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Inert gases (also called the noble gases; group 18) are group of gases located at the rightmost part in the periodic table. They are in that position for a certain purpose that they have completely filled p sub shell which is apparently the most stable configuration for an atom. Consequently, removing an electron in a completely filled shell is harder compared to other elements in the periodic table.

Ionization energy can be simply defined as the energy required in removing an electron in the shell thus forming ions. Since removing an electron from an inert gas is harder compared to other elements, it will have higher ionization energy. 

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givingiswinning | Student, Grade 10 | (Level 1) Valedictorian

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 it is harder for inert gases to lose electrons.

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atyourservice | Student, Grade 11 | (Level 3) Valedictorian

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Because inert gases have all their valence electrons making them stable, as a turn this makes it harder for them to lose electrons.