Question

Use principles established in this chapter to arrange the following atoms in order of increasing value of the first ionization energy: \(\mathrm{Sr}, \mathrm{Cs}, \mathrm{S}, \mathrm{F}, \mathrm{As}.\)

Short answer

The correct order of the atoms from lowest to highest first ionization energy is Cs, Sr, As, S, F.

Step-by-step solution

Locate elements on the periodic table

Identify the positions of Sr (Strontium), Cs (Cesium), S (Sulphur), F (Fluorine), and As (Arsenic) on the periodic table. Strontium and Cesium are in the same group (Group 2), and Cesium is below Strontium. Sulphur, Fluorine, and Arsenic are in different periods but in the same group (Group 16), with Arsenic below Sulphur and Fluorine.

Rank based on groups

According to the ionization energy trend in the periodic table, ionization energy decreases down a group. Therefore, between Strontium and Cesium, Cesium will have the lower ionization energy. Similarly, between Sulphur, Fluorine, and Arsenic, Arsenic will have the lowest ionization energy.

Rank based on periods

Ionization energy increases across a period from left to right. Therefore, between Strontium and Arsenic, Strontium will have lower ionization energy since it is further left on the periodic table. Similarly, between Sulphur and Fluorine, Sulphur will have lower ionization energy since it is further left on the periodic table.

Final arrangement

Based on the steps above, the final arrangement of the atoms from lowest to highest first ionization energy should be: Cs, Sr, As, S, F.

Key concepts

Periodic Table

The periodic table is a comprehensive chart that organizes all known chemical elements based on their atomic number, electron configurations, and recurring chemical properties. This table is structured in such a way that elements are laid out in increasing order of atomic number, from left to right and top to bottom, similar to reading text.

Each row in the periodic table is called a period, and each column is known as a group. The elements in the same group tend to exhibit similar chemical behaviors because they have the same number of valence electrons.

It's crucial for understanding trends in ionization energy, as elements are grouped so recurring trends, known as periodic trends, can be observed more clearly. This structure allows scientists and students alike to predict the behaviors and properties of elements, including how they will interact or bond with other elements.

Group Trends

In the periodic table, elements are arranged into vertical columns called groups. These groups are numbered from 1 to 18. Elements within a group share similar properties and trends due to their similar electron configurations.

One key trend observed within groups is the change in ionization energy, which is the energy required to remove an electron from an atom. As you move down a group, the ionization energy tends to decrease. This is because the outer electrons are farther from the nucleus and experience more electron shielding, making it easier to remove an electron.

For example, in Group 1 (the alkali metals), ionization energy decreases down the group from lithium to cesium. This is a critical concept for predicting and understanding the reactivity and chemical behavior of elements in a group.

Periodic Trends

Periodic trends are patterns in the periodic table that show how certain chemical properties of elements change in predictable ways. These trends help in understanding and predicting the chemical behavior of elements.

One important periodic trend is the ionization energy trend. As you move across a period from left to right, the ionization energy generally increases. This happens because, as protons are added to the nucleus, the nuclear charge increases, pulling the electrons closer to the nucleus and making them harder to remove.

Conversely, as stated earlier, moving down a group usually results in decreased ionization energy due to increased distance from the nucleus and additional electron shielding. Recognizing these trends is essential for solving problems that involve arranging elements based on ionization energy and other chemical properties.

Chemical Elements

Chemical elements are the building blocks of all matter. They are pure substances consisting of only one type of atom and are distinguished by their unique number of protons, called the atomic number.

There are over 100 known chemical elements, and they each have unique properties that can be anticipated when placed in the periodic table. Understanding an element's position on the periodic table provides insight into its properties, such as ionization energy, electronegativity, and atomic radius.

For instance, the problem in the exercise involves comparing five elements: Sr (Strontium), Cs (Cesium), S (Sulfur), F (Fluorine), and As (Arsenic). By locating these elements on the periodic table and applying knowledge of the trends, we can predict and compare their ionization energies, gaining deeper insight into the fundamental behaviors of these elements.