Problem 100 - Chemistry: The Central Science in SI Units, Global Edition

Question

From the following list of elements \(-\mathrm{Mg}, \mathrm{Li}, \mathrm{T}, \mathrm{Pb}, \mathrm{Se}, \mathrm{Cl}, \mathrm{Xe}, \mathrm{Si},\) C-pick the one that best fits each description. Use each element only once: (a) an alkali metal, \((\mathbf{b})\) an alkaline earth metal, \((\mathbf{c})\) a noble gas, (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, (i) an element that is used as radiation shielding.

Step-by-Step Solution

Answer

(a) \(Li\) (b) \(Mg\) (c) \(Xe\) (d) \(Cl\) (e) \(Si\) (f) C (g) \(T\) (h) \(Se\) (i) \(Pb\)

Step 1: An alkali metal

To find an alkali metal, we look for elements in Group 1 of the periodic table. The only element in the given list that is in Group 1 is \(Li\), so \(Li\) is an alkali metal.

Step 2: An alkaline earth metal

To find an alkaline earth metal, we look for elements in Group 2 of the periodic table. The only element in the given list that is in Group 2 is \(Mg\), so \(Mg\) is an alkaline earth metal.

Step 3: A noble gas

To find a noble gas, we look for elements in Group 18 of the periodic table. The only element in the given list that is in Group 18 is \(Xe\), so \(Xe\) is a noble gas.

Step 4: A halogen

To find a halogen, we look for elements in Group 17 of the periodic table. The only element in the given list that is in Group 17 is \(Cl\), so \(Cl\) is a halogen.

Step 5: A metalloid in group 14

To find a metalloid in Group 14, we look for elements in Group 14 that have properties between metals and nonmetals. The only element in the given list that is in Group 14 and is a metalloid is \(Si\), so \(Si\) is a metalloid in group 14.

Step 6: A nonmetal listed in group 14

To find a nonmetal listed in Group 14, we look for elements that have properties of nonmetals and are in Group 14. The only element in the given list that is in Group 14 and is a nonmetal is C, so C is a nonmetal listed in group 14.

Step 7: A metal that forms 3+ ion

To find a metal that forms a 3+ ion, we can look for elements that lose 3 electrons when they form ions. In the given list, \(T\) represents the element Thallium, which can form a 3+ ion as \(T^{3+}\), so \(T\) is a metal that forms a 3+ ion.

Step 8: A nonmetal that forms a 2- ion

To find a nonmetal that forms a 2- ion, we can look for elements that gain 2 electrons when they form ions. In the given list, \(Se\) is a nonmetal that forms a 2- ion as \(Se^{2-}\), so \(Se\) is a nonmetal that forms a 2 - ion.

Step 9: An element that is used as radiation shielding

Among the given elements, the one that is used as radiation shielding is \(Pb\). \(Pb\) is a heavy metal that can absorb and block high-energy radiation such as gamma rays and X-rays, making it a suitable material for radiation shielding.

Key Concepts

Alkali Metals

Alkali metals are fascinating elements located in Group 1 of the periodic table. These include elements like lithium (Li), sodium (Na), and potassium (K). They are known for being highly reactive, especially with water, as they produce hydrogen gas and form strong alkaline hydroxides. Because of their reactivity, alkali metals are never found in their elemental state in nature. They are soft, shiny, and have low melting points compared to other metals.

• Highly reactive, especially with water
• Soft and shiny
• Low melting points

In our example, lithium (Li) is identified as an alkali metal. These metals must be stored under oil to prevent reactions with moisture in the air.

Alkaline Earth Metals

Alkaline earth metals reside in Group 2 of the periodic table and include elements like magnesium (Mg) and calcium (Ca). They too are reactive, although less so than alkali metals. Alkaline earth metals readily form 2+ ions by losing their two outermost electrons. This property makes them essential in various applications, such as the production of cement and the strengthening of alloys.

• Form 2+ ions
• Relatively less reactive than alkali metals
• Important in alloy production

Magnesium (Mg), chosen in our exercise, is commonly involved in biological processes and is crucial for animal and plant life.

Noble Gases

Noble gases, found in Group 18, are known for their remarkable lack of reactivity. This group includes elements like helium (He), neon (Ne), and xenon (Xe), which is specified in our exercise. Because of their full valence shell of electrons, noble gases are incredibly stable and rarely engage in chemical reactions.

• Inert and nonreactive
• Full valence electron shells
• Useful in lighting and refrigeration

These gases are colorless, odorless, and nonflammable, being used widely in applications such as lighting (neon lights) and cryogenics (helium).

Metalloids

Metalloids are elements with properties that fall between those of metals and nonmetals, often displaying a mix of physical and chemical characteristics. Silicon (Si) is a prime example of a metalloid, notably used in semiconductor technology because it can conduct electricity under certain conditions. Metalloids reside in a zig-zag line between metals and nonmetals on the periodic table, making them invaluable in the electronics industry.

• Exhibit both metallic and nonmetallic properties
• Found in a zig-zag line in the periodic table
• Critical in semiconductor technology

Silicon's application in chips and electronics stems from its nature as a semiconductor, allowing it to efficiently control electrical flow.

Halogens

Halogens, located in Group 17 of the periodic table, are known for their high reactivity. They include elements like chlorine (Cl), fluorine (F), and iodine (I). These elements are especially known for forming salts when they react with metals. For instance, sodium chloride (table salt) is formed when chlorine combines with sodium.

• Highly reactive
• Form salts with metals
• Exist in various physical states at room temperature

Chlorine, used in pool sanitation and water purification, is just one example from our exercise. Its reactivity is harnessed in many industrial and domestic cleaning products.