Question

From the following list of elements \(-\mathrm{Mg}, \mathrm{Li}, \mathrm{Tl}, \mathrm{Pb}, \mathrm{Se}, \mathrm{Cl}, \mathrm{Xe}, \mathrm{Si},\) C-pick the one that best fits each description. Use each element only once: \((\mathbf{a})\) an alkali metal, \((\mathbf{b})\) an alkaline earth metal, \((\mathbf{c})\) a noble gas, \((\mathbf{d})\) a halogen, \((\mathbf{e})\) a metalloidin group \(14,(\mathbf{f})\) a nonmetal listed in group \(14,(\mathbf{g})\) a metal that forms a \(3+\) ion, \((\mathbf{h})\) a nonmetal that forms a \(2-\) ion, \((\mathbf{i})\) an element that is used as radiation shielding.

Short answer

(a) Li, (b) Mg, (c) Xe, (d) Cl, (e) Si, (f) C, (g) Tl, (h) Se, (i) Pb.

Step-by-step solution

Identify an alkali metal

Alkali metals are group 1 elements. From the list, the only alkali metal is lithium (Li).

Identify an alkaline earth metal

Alkaline earth metals are group 2 elements. Magnesium (Mg) is the only alkaline earth metal in the list.

Identify a noble gas

Noble gases are group 18 elements. Xenon (Xe) is the only noble gas present in the list.

Identify a halogen

Halogens are group 17 elements. Chlorine (Cl) is the halogen contained in the list.

Identify a metalloid in group 14

Metalloids have properties of both metals and nonmetals. Silicon (Si) is the group 14 metalloid among the listed elements.

Identify a nonmetal in group 14

Carbon (C) is a nonmetal found in group 14.

Identify a metal that forms a 3+ ion

Thalium (Tl) is a metal known to form a 3+ ion.

Identify a nonmetal that forms a 2− ion

Selenium (Se) is a nonmetal that can form a 2− ion.

Identify an element used as radiation shielding

Lead (Pb) is commonly used as radiation shielding due to its high density.

Key concepts

Alkali Metals

Alkali metals are fascinating elements that can be found in Group 1 of the periodic table. These metals are incredibly reactive. The common alkali metals include lithium (Li), sodium (Na), and potassium (K). Because of their high reactivity, they are always found in nature combined with other elements rather than in their pure form.
Some characteristics of alkali metals include:

• Soft consistency and can often be cut with a knife.
• Shiny appearance but tarnish quickly when exposed to air.
• React vigorously with water to form hydrogen gas and alkaline solutions.

Alkali metals have a single electron in their outer shell, which makes them want to lose that electron and form a positively charged ion (e.g., Li becomes Li⁺). This makes them highly reactive and quite essential in many chemical processes.

Alkaline Earth Metals

Alkaline earth metals are found in Group 2 of the periodic table and include elements such as magnesium (Mg) and calcium (Ca). These metals are known for being somewhat reactive, though less so than alkali metals.
Here are some notable properties of alkaline earth metals:

• Harder and denser compared to alkali metals.
• React with water, though not as vigorously as alkali metals do.
• Commonly form compounds like oxides and chlorides that are found in the earth's crust.

Alkaline earth metals typically lose two electrons to form divalent cations, such as Mg²⁺, making them vital in various biological and industrial applications. Magnesium, for example, is crucial for plant and animal life.

Noble Gases

Noble gases are a unique group of elements found in Group 18 of the periodic table. They include helium (He), neon (Ne), and xenon (Xe), recognized for their lack of reactivity. This unreactive nature is due to them having a full outer electron shell, which makes them stable and less inclined to form chemical bonds.
Some key characteristics of noble gases:

• Colorless, odorless, and tasteless under standard conditions.
• Known for not forming compounds easily, but some can form under extreme conditions.
• Used in lighting and signs due to their ability to emit bright colors when electrically charged.

Because they are so inert, they serve vital roles in non-reactive environments, such as filling light bulbs and as carriers of sensitive materials.

Halogens

Halogens can be found in Group 17 of the periodic table, including elements such as fluorine (F), chlorine (Cl), and iodine (I). Known for being the most reactive nonmetals, halogens readily form salts with metals.
Key features of halogens include:

• Exist as diatomic molecules in their elemental form (e.g., Cl₂).
• Vary in color; for instance, chlorine is yellow-green, while iodine is dark purple.
• Highly electronegative, which means they have a strong tendency to gain an electron and form negative ions.

Halogens are extremely effective as disinfectants and are widely used in cleaning products and water treatment facilities. They also play critical roles in biological functions and the development of pharmaceuticals.

Metalloids

Metalloids are a category of elements that have properties intermediate between metals and nonmetals. Elements such as silicon (Si) and germanium (Ge) are classic metalloids.
Some distinctive traits of metalloids include:

• Ability to conduct electricity better than nonmetals but not as well as metals, making them semiconductors.
• Often used in the electronics industry, with silicon being integral in the manufacture of computer chips.
• Exist in various allotropic forms, allowing for diverse applications.

Metalloids usually have a mixed collection of chemical behaviors, reacting differently based on the chemicals they interact with. This characteristic allows them to be versatile elements in scientific and industrial applications.

Nonmetals

Nonmetals are a diverse set of elements found throughout the periodic table, marked by their lack of metallic characteristics. Examples include carbon (C) and oxygen (O). Nonmetals make up most of the Earth's crust and atmosphere.
Here's what differentiates nonmetals:

• Generally poor conductors of heat and electricity.
• Brittle in solid form, so they break easily rather than bending.
• Often gain electrons in chemical reactions to form anions.

Nonmetals play crucial roles in life and industry. For instance, carbon is fundamental to all known life forms, and oxygen is essential for respiration. Their varied reactivity makes them vital in creating a multitude of compounds.

Radiation Shielding

Radiation shielding materials are critical in protecting against harmful radiation from natural and man-made sources. Lead (Pb) is one of the most effective and commonly used materials for this purpose.
Some characteristics of lead when used as a shielding material are:

• High density, which makes it highly effective in absorbing radiation.
• Malleable nature, allowing it to be shaped into various forms to suit different shielding needs.
• Used extensively in medical settings for radiation protection and in the construction of nuclear facilities.

Using lead as radiation shielding is essential in industries where radiation exposure is high, ensuring safety and minimizing health risks.

Ion Formation

Ion formation occurs when an atom gains or loses electrons, resulting in a net positive or negative charge. This process is crucial in chemical reactions and the formation of compounds.
Key points about ion formation:

• Cations are positive ions formed by the loss of electrons, commonly by metals. For example, Tl can form a +3 cation (Tl³⁺).
• Anions are negative ions formed by the gain of electrons, usually by nonmetals. Selenium (Se), for example, can form a -2 anion (Se²⁻).
• Ion formation helps explain the bonding and structure of compounds, as ions often combine to neutralize their charges and form stable substances.

This concept is foundational in understanding how elements interact chemically, leading to the endless variety of materials and chemicals we encounter in our daily lives.