Question

Only a few atoms of astatine, At, atomic number \(85,\) have been detected. On the basis of its position on the periodic table, would you expect it to be a metal or a nonmetal?

Short answer

Astatine is expected to be a nonmetal.

Step-by-step solution

Identify the Periodic Table Group

Astatine (At) is located in Group 17 of the periodic table, which is also known as the halogens group. Examples of other elements in this group are fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

Analyze Common Characteristics of Group 17

The elements in Group 17 share similar properties: they are all nonmetals, are typically insulators, and have high electronegativity values, making them reactive, especially with alkali metals and alkaline earth metals.

Compare Astatine to Other Halogens

Astatine, like other halogens, is expected to have nonmetallic properties, even though its metallic characteristics might increase due to its larger atomic size compared to other halogens.

Conclude Based on Group Characteristics

Given its position in the halogen group and the properties typical of this group, astatine would be expected to be a nonmetal.

Key concepts

Halogens

Halogens are a fascinating group of elements located in Group 17 of the periodic table. These include fluorine, chlorine, bromine, iodine, and astatine. Known for their high reactivity, halogens are nonmetals, which means they do not conduct electricity well and are not ductile or malleable.

Halogens have some unique characteristics. They have the highest electronegativities in their respective periods, which means they are highly effective in attracting electrons from other elements to form compounds. This property makes them particularly reactive, especially with alkali metals, with which they form halide salts such as sodium chloride (NaCl). Additionally, their reactivity decreases as you move down the group from fluorine to astatine.

In nature, halogens are usually found as compounds rather than isolated elements due to their high reactivity. They have a variety of uses, from purifying water with chlorine to using iodine in antiseptics.

Nonmetals

Nonmetals are elements that contrast greatly with metals in terms of their physical properties. Found on the right side of the periodic table, they share certain characteristics such as being poor conductors of heat and electricity. This makes them excellent insulators in many applications.

Nonmetals can form both ionic and covalent bonds. When they gain electrons, they form anions in ionic compounds, as seen in halide compounds formed by halogens. In their covalent form, they share electrons with other nonmetals, forming molecules like water (H₂O) and carbon dioxide (CO₂).

These elements possess a wide range of uses. For instance, sulfur is used in vulcanizing rubber, while nitrogen is essential for the synthesis of ammonia for fertilizers. Understanding the properties of nonmetals is crucial in fields ranging from chemistry to environmental science.

Group 17 Elements

Group 17 elements, which encompass the halogens, are known for their distinctive properties. Located at the penultimate column of the periodic table, they play a critical role in both natural and industrial processes.

The elements in this group are characterized by having seven valence electrons. This configuration makes them just one electron short of having a full outer shell, driving their reactivity as they tend to gain an electron to achieve stability. Due to this tendency, the reactivity of halogens typically results in the formation of various compounds.

Furthermore, these elements exhibit trends in their physical states as well. As you move down the group from fluorine to iodine, the elements transition from gases to solids at room temperature. This change is due to increasing atomic size and molecular weights. Understanding these trends is essential when analyzing the behavior and applications of Group 17 elements in various chemical reactions.