Question
What is the ionization potential of atomic hydrogen and why is the first ionization energy of chlorine greater than that of lithium?
Answers
GPT-4o mini
The ionization potential (or ionization energy) of atomic hydrogen is approximately 13.6 electron volts (eV). This energy is the amount required to remove the electron from a hydrogen atom, resulting in a hydrogen ion (H⁺).
Regarding the first ionization energy of chlorine being greater than that of lithium, there are several key factors at play:
1. **Atomic Structure**: Lithium (Li) has an atomic number of 3, which means it has three protons and, in its neutral state, three electrons (configuration: 1s² 2s¹). Chlorine (Cl), with an atomic number of 17, has 17 protons and 17 electrons (configuration: 1s² 2s² 2p⁶ 3s² 3p⁵). The outer electron of lithium is in the 2s orbital, whereas chlorine has additional electrons in full 2p orbitals and is more compactly packed.
2. **Effective Nuclear Charge**: The effective nuclear charge experienced by outer electrons is higher in chlorine compared to lithium. Chlorine has more protons (17) than lithium (3), so the electrons in chlorine experience a stronger attraction to the nucleus despite being farther from it. This higher effective nuclear charge in chlorine means that its outer electrons are held more tightly.
3. **Electron Shielding**: In lithium, the outer electron (2s) feels the effects of shielding from only two inner electrons (1s²), whereas in chlorine, the outermost electrons are shielded by a complete electron shell (1s² 2s² 2p⁶) which adds to the shielding effect. However, because there are more protons pulling on the valence electrons in chlorine, the net effect is that chlorine’s outer electrons are still held more tightly than those in lithium.
Therefore, the combination of a higher effective nuclear charge and more stable electron configuration leads to the first ionization energy of chlorine being greater than that of lithium. The first ionization energy of lithium is about 5.39 eV, while that of chlorine is about 12.97 eV.
Regarding the first ionization energy of chlorine being greater than that of lithium, there are several key factors at play:
1. **Atomic Structure**: Lithium (Li) has an atomic number of 3, which means it has three protons and, in its neutral state, three electrons (configuration: 1s² 2s¹). Chlorine (Cl), with an atomic number of 17, has 17 protons and 17 electrons (configuration: 1s² 2s² 2p⁶ 3s² 3p⁵). The outer electron of lithium is in the 2s orbital, whereas chlorine has additional electrons in full 2p orbitals and is more compactly packed.
2. **Effective Nuclear Charge**: The effective nuclear charge experienced by outer electrons is higher in chlorine compared to lithium. Chlorine has more protons (17) than lithium (3), so the electrons in chlorine experience a stronger attraction to the nucleus despite being farther from it. This higher effective nuclear charge in chlorine means that its outer electrons are held more tightly.
3. **Electron Shielding**: In lithium, the outer electron (2s) feels the effects of shielding from only two inner electrons (1s²), whereas in chlorine, the outermost electrons are shielded by a complete electron shell (1s² 2s² 2p⁶) which adds to the shielding effect. However, because there are more protons pulling on the valence electrons in chlorine, the net effect is that chlorine’s outer electrons are still held more tightly than those in lithium.
Therefore, the combination of a higher effective nuclear charge and more stable electron configuration leads to the first ionization energy of chlorine being greater than that of lithium. The first ionization energy of lithium is about 5.39 eV, while that of chlorine is about 12.97 eV.