The correct answer is A. There is an increase in the nuclear charge of the alkaline earth metals.
Explanation:
1. Ionization energy is the energy required to remove an electron from an atom or ion in the gaseous state.
2. Alkali metals and alkaline earth metals are two groups in the periodic table with different properties.
3. Alkali metals are found in Group 1 of the periodic table, while alkaline earth metals are found in Group 2.
4. Alkaline earth metals have higher first ionization energies compared to alkali metals because they have an extra electron shell and therefore experience a greater effective nuclear charge.
5. The effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom. It increases as you move across a period from left to right in the periodic table.
6. Therefore, the increase in the nuclear charge of the alkaline earth metals leads to higher first ionization energies compared to the alkali metals.
