Which element in the periodic table has the largest first ionization energy?

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Understand that ionization energy is the energy required to remove an electron from an atom in the gaseous state.

Recall that ionization energy generally increases across a period (from left to right) on the periodic table due to increasing nuclear charge and decreasing atomic radius.

Remember that ionization energy generally decreases down a group (from top to bottom) because of increasing atomic radius and electron shielding.

Identify that the element with the largest first ionization energy will be located at the top right corner of the periodic table, excluding the noble gases.

Conclude that among the elements, the one with the largest first ionization energy is likely to be a halogen or a non-metal in the second period.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. It is a key indicator of how strongly an atom holds onto its electrons. Generally, ionization energy increases across a period in the periodic table due to increasing nuclear charge and decreases down a group due to increased distance from the nucleus and electron shielding.

Periodic Trends

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across or down the periodic table. For ionization energy, the trend shows that it increases from left to right across a period and decreases from top to bottom in a group. Understanding these trends helps in predicting the ionization energies of different elements.

Noble Gases

Noble gases, located in Group 18 of the periodic table, are known for their high ionization energies and low reactivity due to their full valence electron shells. Among the elements, helium has the highest first ionization energy, followed closely by neon. Their stable electron configurations make them less likely to lose electrons, contributing to their high ionization energies.

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Related Practice

Textbook Question

Which element has the highest second ionization energy: Li, K, or Be?

Textbook Question

Identify each statement as true or false.

a. Ionization energies are always negative quantities.

b. Oxygen has a larger first ionization energy than fluorine.

c. The second ionization energy of an atom is always greater than its first ionization energy.

d. The third ionization energy is the energy needed to ionize three electrons from a neutral atom.

Textbook Question

Pick the correct word to complete the sentence: The larger the atom, the (smaller/larger) its first ionization energy.

Textbook Question

Would a neutral K atom or a K+ ion have a more negative value of electron affinity?