Question

The first four ionization energies of an element are approximately \(738,1450,7.7 \times 10^{3},\) and \(1.1 \times 10^{4} \mathrm{~kJ} / \mathrm{mol}\). To which periodic group does this element belong? Explain your answer.

Short answer

The element belongs to Group 2 (alkaline earth metals) due to the ionization energy pattern with a large increase after the second ionization energy.

Step-by-step solution

Understanding Ionization Energy

Ionization energy is the amount of energy required to remove an electron from an atom or ion. Elements with low ionization energy tend to lose electrons easily, whereas those with high ionization energy hold onto their electrons tightly.

Analyzing the Ionization Energies

Looking at the ionization energies provided: 738 kJ/mol (1st), 1450 kJ/mol (2nd), 7700 kJ/mol (3rd), and 11000 kJ/mol (4th). The first two energies are relatively low compared to the dramatic increase at the 3rd ionization energy.

Identifying the Group Based on the Large Jump

The large jump in ionization energy between the 2nd and 3rd values suggests that the third electron is being removed from a new, more stable electron shell. Usually, this type of jump is indicative of moving from a filled outer shell to the next inner shell.

Matching to Periodic Groups

The large increase after the second ionization energy indicates the element has two electrons in its outer shell, as removing a third electron is significantly harder because it involves breaking into a filled inner shell. This pattern matches alkaline earth metals, which belong to Group 2 of the periodic table.

Key concepts

Alkaline Earth Metals

Alkaline earth metals are a group of elements found in Group 2 of the periodic table. These elements include beryllium, magnesium, calcium, strontium, barium, and radium. They all have two electrons in their outermost shell which they readily lose to form positive ions. This characteristic gives them similar properties.
- These metals tend to be highly reactive, although their reactivity is less than that of the alkali metals found in Group 1.
- Due to their two valence electrons, they form ionic compounds with nonmetals and are often found in various minerals in the earth’s crust.
- They exhibit a shiny, silvery luster and are good conductors of electricity and heat.
Understanding the properties of alkaline earth metals helps explain their role in various industrial and chemical applications.

Periodic Table

The periodic table is a systematic arrangement of elements, showcasing patterns in their behavior. Arranged by increasing atomic number, the periodic table helps predict properties of elements based on their position.
- Each element in the periodic table is represented by a unique symbol and is placed within a specific "group" or "period".
- Groups are the vertical columns and indicate elements that have similar chemical properties due to having the same number of electrons in their outer shell.
- Periods are the horizontal rows where elements have the same number of electron shells.
This structured table allows chemists and students to easily compare elements and predict how they will interact with one another.

Electron Shells

Electron shells refer to the layers surrounding the nucleus of an atom where electrons are likely to be found. These shells are crucial in determining an element's reactivity and how it bonds with other elements.
- Electrons are arranged in shells based on rules of quantum mechanics, and each shell can hold a specific maximum number of electrons.
- The outermost shell, known as the valence shell, is significant for chemical reactivity and bonding, as its electrons are involved in these processes.
- Moving to elements with higher atomic numbers, electrons populate more shells, which influences the element's chemical behavior.
Understanding electron shells is fundamental for grasping how and why elements combine and react chemically.

Ionization Process

Ionization energy refers to the energy required to remove an electron from an atom or ion, indicating how strongly an atom holds onto its electrons. The process of ionization is essential for forming ions from atoms.
- First ionization energy refers to the energy needed to remove the outermost electron.
- Each subsequent ionization energy becomes significantly higher as the electrons are more strongly attracted by the nucleus.
- Large jumps in ionization energy often indicate the removal of an electron from a closer, more filled shell.
Understanding the ionization process helps in identifying an element's place in the periodic table and predicting its chemical properties based on its ionization energies.