The first and second ionization energy are the energy required to remove the first and second electron from an atom, respectively.

The first ionization energy is the energy required to remove the first electron from an atom in its gaseous state. This energy is dependent on the atomic radius, nuclear charge, and electron shielding. As the atomic radius increases, the first ionization energy decreases because the outermost electron is farther from the nucleus and experiences less attraction. As the nuclear charge increases, the first ionization energy increases because the outermost electron is held more tightly. Electron shielding also affects the first ionization energy, as more shielding leads to a decrease in the effective nuclear charge felt by the outermost electron.

The second ionization energy is the energy required to remove the second electron from an atom that has already lost its first electron. This energy is higher than the first ionization energy because the atom is now positively charged and the remaining electrons are held more tightly. The second ionization energy is also affected by the electron configuration of the atom, as removing an electron from a filled or half-filled subshell requires more energy than removing an electron from an unfilled subshell.

Overall, the first and second ionization energies are important in understanding the reactivity and chemical properties of elements. Elements with low first ionization energies tend to be more reactive, while elements with high second ionization energies tend to form cations with a high charge.


A Level

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