Question

For each of the following pairs, indicate which element has the smaller first ionization energy: (a) \(\mathrm{Cs}, \mathrm{Cl} ;(\mathbf{b}) \mathrm{Fe}, \mathrm{Zn} ;\) (c) \(\mathrm{I}, \mathrm{Cl} ;(\mathbf{d}) \mathrm{Se}, \mathrm{Sn}\)

Short answer

For each pair: (a) Cs has the smaller first ionization energy. (b) Fe has the smaller first ionization energy. (c) I has the smaller first ionization energy. (d) Sn has the smaller first ionization energy.

Step-by-step solution

Periodic Table Position

Locate Cs and Cl on the periodic table. Cs belongs to the alkali metal group (Group 1) and Cl belongs to the halogen group (Group 17).

Evaluate Ionization Energy Trend

Ionization energy increases from left to right across a period. Since Cl is located to the right of Cs within the same period, Cl has a higher first ionization energy than Cs. Thus, Cs has the smaller first ionization energy. #b) Fe vs Zn#

Periodic Table Position

Locate Fe and Zn on the periodic table. Both Fe (Iron) and Zn (Zinc) are part of the same period and belong to the transition metal group.

Evaluate Ionization Energy Trend

Ionization energy increases from left to right across a period. Since Fe is located to the left of Zn within the same period, Fe has a smaller first ionization energy than Zn. #c) I vs Cl#

Periodic Table Position

Locate I and Cl on the periodic table. Both elements belong to the halogen group (Group 17) and are in different periods.

Evaluate Ionization Energy Trend

Ionization energy decreases from top to bottom within a group. Since I is located below Cl within the same group, I has a smaller first ionization energy than Cl. #d) Se vs Sn#

Periodic Table Position

Locate Se and Sn on the periodic table. Se belongs to the Chalcogen group (Group 16) and Sn belongs to the Carbon group (Group 14).

Evaluate Ionization Energy Trend

Ionization energy decreases from top to bottom within a group and increases from left to right across a period. Since Se is located above and to the right of Sn, Se has a higher first ionization energy than Sn. Thus, Sn has the smaller first ionization energy.

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 chemical properties. It arranges elements in rows called periods and columns called groups or families. The periodic table is a valuable tool for predicting the properties and behaviors of elements.

• Periods: Horizontal rows that indicate increasing atomic numbers and repeating patterns in element properties.
• Groups: Vertical columns that group elements with similar chemical characteristics.
• Trends: The periodic table displays trends such as atomic radius, electronegativity, and ionization energy.

Understanding these arrangements and patterns helps chemists predict how elements will react and combine with one another.

Alkali Metals

Alkali metals are a group of elements located in Group 1 of the periodic table. They include elements like lithium (Li), sodium (Na), potassium (K), and cesium (Cs). These metals are known for their high reactivity and tendency to lose one electron to form positive ions.

• Properties: Soft, shiny, with low densities, and low melting points.
• Reactivity: Highly reactive, especially with water, and increase in reactivity down the group.
• Ionization Energy: Alkali metals have low first ionization energies, which means they easily give up their outermost electron.

Due to their reactivity, alkali metals are rarely found in their elemental state in nature.

Halogens

Halogens are found in Group 17 of the periodic table and are known for their high reactivity. The group includes fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). These elements are rich in unique properties due to their seven electrons in the outermost shell, making it easy to gain an additional electron.

• Properties: Non-metals, with varying colors and states at room temperature (e.g., F is a pale yellow gas, Cl is a green gas).
• Reactivity: Extremely reactive, particularly with alkali metals and alkaline earth metals, forming salts like sodium chloride (NaCl).
• Ionization Energy: Halogens generally have high ionization energies, but within the group, it decreases from top to bottom.

Halogens are essential in many applications, including disinfection and in the synthesis of organic compounds.

Transition Metals

Transition metals occupy the central block of the periodic table, between Groups 3 and 12. This group includes elements such as iron (Fe), copper (Cu), and zinc (Zn). They are characterized by their ability to form positive ions with various charges.

• Properties: Typically hard, with high melting and boiling points, and are good conductors of electricity.
• Reactivity: They display varying reactivity with different elements and compounds, forming colorful compounds.
• Ionization Energy: Transition metals have moderate first ionization energies, which allow for the removal of their outermost electron.

These metals are critical in construction, manufacturing, and as catalysts in many chemical reactions.