Question

Which has the larger second ionization energy, lithium or beryllium? Why?

Short answer

Lithium has the larger second ionization energy compared to Beryllium. The second ionization of lithium involves removing an electron from the tightly held inner shell, while for beryllium, it requires removing an electron from the less tightly held \(2s\) shell. This difference in energy required is due to the strong attraction between the electrons in the \(1s\) shell and the nucleus in lithium, whereas in beryllium, the electron is farther away from the nucleus and experiences less attraction.

Step-by-step solution

Write the electronic configurations of lithium and beryllium atoms

: First, we need to write the electronic configurations of lithium and beryllium atoms by filling orbitals in order of increasing energy levels: Lithium (Li) - Atomic number: 3 Electronic configuration: \(1s^{2}2s^{1}\) Beryllium (Be) - Atomic number: 4 Electronic configuration: \(1s^{2}2s^{2}\)

Compare their first ionization energies

: Now let's compare their first ionization energies by considering the factors influencing ionization energy: size of the atom, nuclear charge, and electron shielding. First Ionization energy of Li: According to Li's electronic configuration, the electron removed during the first ionization is from the \(2s^{1}\) orbital. This electron is relatively easy to remove due to its distance from the nucleus and weak shielding effect from the \(1s^{2}\) electrons. First Ionization energy of Be: In the case of Be, the electron removed during the first ionization is also from the \(2s\) orbital, but due to a higher nuclear charge (+4 in Be vs. +3 in Li), the first ionization energy of Be is greater than that of Li.

Compare their second ionization energies

: To compare their second ionization energies, we will be removing another electron from each ion and consider the factors discussed earlier. Second Ionization energy of Li: After the first ionization, Li remains with electronic configuration \(1s^{2}\). Now, to remove the second electron, we need to overcome the strong attraction between the electrons in the \(1s\) shell and the nucleus, resulting in a large second ionization energy. Second Ionization energy of Be: After the first ionization, Be remains with electronic configuration \(1s^{2}2s^{1}\). To remove the second electron, which is in the \(2s\) shell, we need less energy compared to removing an electron from the inner shell as in Li's case.

Conclusion

: Comparing the second ionization energies of lithium and beryllium, Lithium's second ionization energy involves removing an electron from the tightly held inner shell, resulting in a larger second ionization energy. Beryllium's second ionization energy involves removing an electron from the less tightly held \(2s\) shell, requiring less energy than Li. Therefore, Lithium has the larger second ionization energy compared to Beryllium.