Ionization Potential in Li and He

Introduction
Ionization potential, also known as ionization energy, is the energy required to remove an electron from an atom or ion in its ground state. It is an important property that determines the reactivity and chemical behavior of elements. In this response, we will compare the ionization potential of lithium (Li) and helium (He) and determine which element has the greater ionization potential.

Ionization Potential
Ionization potential is influenced by several factors, including the atomic structure and the effective nuclear charge experienced by the outermost electron. The effective nuclear charge is the net positive charge experienced by an electron due to the attraction of the protons in the nucleus, which is mitigated by the shielding effect of inner electrons.

Atomic Structure
Lithium (Li)
- Atomic number: 3
- Electronic configuration: 1s² 2s¹
- Lithium has three protons in its nucleus and two inner electrons shielding the outermost electron.

Helium (He)
- Atomic number: 2
- Electronic configuration: 1s²
- Helium has two protons in its nucleus and zero inner electrons shielding the outermost electron.

Comparison
Shielding Effect
The shielding effect of inner electrons reduces the effective nuclear charge experienced by the outermost electron, making it easier to remove. In Li, the outermost electron experiences a greater effective nuclear charge compared to He, as there are two inner electrons shielding the outermost electron in Li, while He has no inner electrons.

Atomic Radius
The atomic radius also plays a role in determining ionization potential. As the atomic radius increases, the outermost electron is further away from the nucleus, reducing the effective nuclear charge experienced by the electron. Li has a larger atomic radius compared to He due to the addition of an extra electron shell.

Conclusion
Considering the factors mentioned above, lithium (Li) has a lower ionization potential compared to helium (He). Li has a larger atomic radius and experiences a greater effective nuclear charge due to the presence of inner electrons. Therefore, it requires less energy to remove an electron from Li compared to He.