Question

The first ionization energies of alkaline earth metals are higher than those of alkali metals. This is because (1) there is increase in the nuclear charge of the alkaline earth metals (2) there is decrease in the nuclear charge of alkaline earth metals (3) there is no change in the nuclear charge (4) none of the above

Short answer

The first ionization energies of alkaline earth metals are higher because there is an increase in the nuclear charge (Option 1).

Step-by-step solution

- Understand Ionization Energy

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. For example, the first ionization energy is the energy needed to remove the first electron.

- Compare Alkaline Earth Metals and Alkali Metals

Alkaline earth metals are found in Group 2 of the periodic table, whereas alkali metals are found in Group 1. Alkaline earth metals have two valence electrons, while alkali metals have only one.

- Analyze Nuclear Charge

Nuclear charge refers to the total charge of the nucleus, which increases with the number of protons. As you move from left to right across the periodic table, the nuclear charge increases.

- Relation Between Nuclear Charge and Ionization Energy

Higher nuclear charge means the electrons are held more tightly by the nucleus, making it harder to remove an electron. Therefore, the ionization energy would be higher for elements with a greater nuclear charge.

- Conclusion

Alkaline earth metals have a higher nuclear charge compared to alkali metals in the same period. Therefore, their first ionization energies are higher.

Key concepts

alkaline earth metals

Alkaline earth metals include elements like beryllium, magnesium, calcium, strontium, barium, and radium. These elements are located in Group 2 of the periodic table.
What sets them apart is that they each have two valence electrons in their outermost shell. This makes them less reactive compared to alkali metals, which have only one valence electron.
Alkaline earth metals are shiny and silvery-white and are less reactive compared to the alkali metals. However, their reactivity still increases as you go down the group. For example, magnesium is less reactive than calcium.
The higher ionization energy of alkaline earth metals compared to alkali metals is because of their two valence electrons and increased nuclear charge, which holds these electrons more tightly.

alkali metals

Alkali metals are in Group 1 of the periodic table and include lithium, sodium, potassium, rubidium, cesium, and francium. These elements have only one valence electron, making them extremely reactive.
They are soft metals and can be cut easily with a knife. Alkali metals are known for their vigorous reactions with water, forming strong bases like sodium hydroxide.
Due to having only one valence electron, they are more willing to lose that electron to achieve a stable electronic configuration. This results in lower ionization energies compared to alkaline earth metals.
Additionally, because they have only one electron to remove, the nuclear charge effect is lower, making it easier to ionize them.

nuclear charge

Nuclear charge is the total positive charge in the nucleus of an atom, which comes from the protons. The greater the number of protons, the higher the nuclear charge.
As you move across the periodic table from left to right, the nuclear charge increases because more protons are added to the nucleus. This higher nuclear charge pulls the electrons closer to the nucleus, making them harder to remove.
In the context of ionization energy, a higher nuclear charge means a stronger attraction between the nucleus and the outer electrons. Therefore, more energy will be needed to remove an electron, leading to higher ionization energy.
For alkaline earth metals, a higher nuclear charge compared to alkali metals in the same period means they hold their electrons more tightly, resulting in higher ionization energies.