Ionization Energy [ENDORSED]

[MichelleKaku1H]

To clarify, ionization energy is the energy needed to remove an electron from an atom? Is this a consistent number for each atom? Or does it depend on the situation? Or basically, is it known? Or does it need to be solved for?

[Nicole Nikolov 1K]

Yes, ionization energy is the energy required to remove an electron from an atom. Ionization energies differ for each element, generally increasing across a period and decreasing down a group. The ionization energy for an element will always be the same if, for example, it is the first electron you are removing. However, successive ionization energies will always be higher than the first. Most likely we will be provided with the ionization energies for this class.

[Hellen Truong 2J]

To rephrase, ionization energy is the energy an atom needs to form an ion. Ionization energies are specific to elements, but they get higher each successive electron removal because of shielding. After the first electron is removed, all the other electrons experience a stronger pull, so the second ionization energy is higher.

[Phillip Winters 2F]

Also, ionization energy increases going from left to right on the periodic table because there is a greater effective nuclear charge and the electrons are more attracted to the nucleus of the atom, thus it requires more energy to remove the electrons.

[Diane Bui 2J]

Also, just to add onto everyone else's responses, ionization energy is the minimum energy needed to remove an electron in its gas phase. This is different from the threshold energy that we learned about in the photoelectric effect, which is the energy needed to remove an electron from a metal. Second ionization energy is also significantly higher than first ionization energy due to the electrons being more tightly bounded to the nucleus.

[Katie Lam 1B]

The second ionization energy is also higher than the first because there is less shielding.