Question

Captain Kirk has set a trap for the Klingons who are threatening an innocent planet. He has sent small groups of fighter rockets to sites that are invisible to Klingon radar and put a decoy in the open. He calls this the “fishhook” strategy. Mr. Spock has sent a coded message to the chemists on the fighters to tell the ships what to do next. The outline of the message is Fill in the blanks of the message using the following clues. (1) Symbol of the halogen whose hydride has the second highest boiling point in the series of HX compounds that are hydrogen halides. (2) Symbol of the halogen that is the only hydrogen halide, HX, that is a weak acid in aqueous solution. (3) Symbol of the element whose existence on the sun was known before its existence on earth was discovered. (4) The Group 5A element in Table 20.13 that should have the most metallic character. (5) Symbol of the Group 6A element that, like selenium, is a semiconductor. (6) Symbol for the element known in rhombic and monoclinic forms. (7) Symbol for the element that exists as diatomic molecules in a yellow-green gas when not combined with another element. (8) Symbol for the most abundant element in and near the earth’s crust. (9) Symbol for the element that seems to give some protection against cancer when a diet rich in this element is consumed. (10) Symbol for the smallest noble gas that forms compounds with fluorine having the general formula \(\mathrm{AF}_{2}\) and \(\mathrm{AF}_{4}\) (reverse the symbol and split the letters as shown). (11) Symbol for the toxic element that, like phosphorus and antimony, forms tetrameric molecules when uncombined with other elements (split the letters of the symbol as shown). (12) Symbol for the element that occurs as an inert component of air but is a very prominent part of fertilizers and explosives.

Short answer

The elements corresponding to each clue are as follows: (1) Br, (2) F, (3) He, (4) Bi, (5) Te, (6) S, (7) Cl, (8) O, (9) Se, (10) Xe, (11) As, and (12) N.

Step-by-step solution

Identify the Halogen with the Second Highest Boiling Point

The halogens are found in Group 7 of the Periodic Table. Their hydrides are formed with hydrogen - HX. Looking at the series of these, the halogen with the second highest boiling point is Bromine (Br). So the symbol to fill in the blank for clue (1) is Br.

Identify the Halogen that is a Weak Acid

The halogen that forms a weak acid with hydrogen in an aqueous solution is Fluorine (F). Therefore, the symbol to fill in the blank for clue (2) is F.

Identify the Element Discovered on the Sun before Earth

The element that was discovered on the Sun before its presence was found on Earth is Helium (He). The symbol to fill in the blank for clue (3) is He.

Identify the Most Metallic Group 5A Element

In Group 5A, the element with the most metallic character is Bismuth (Bi). The symbol to fill in the blank for clue (4) is Bi.

Identify the Group 6A Semiconductor Element

The element in Group 6A that behaves as a semiconductor, like selenium, is Tellurium (Te). The symbol that to fill in the blank for clue (5) is Te.

Identify the Element Known in Rhombic and Monoclinic Forms

The element that exists in both rhombic and monoclinic forms is Sulfur (S). The symbol to fill in the blank for clue (6) is S.

Identify the Element that Exists as Diatomic Molecules

The element that exists as diatomic molecules in a yellow-green gas is Chlorine (Cl). The symbol to fill in the blank for clue (7) is Cl.

Identify the Most Abundant Element in Earth's Crust

The most abundant element in and near the Earth’s crust is Oxygen (O). The symbol to fill in the blank for clue (8) is O.

Identify the Element believed to have Cance-Preventive Properties

The element that seems to offer some protection against cancer when consumed in a diet is Selenium (Se). The symbol to fill in the blank for clue (9) is Se.

Identify the Smallest Noble Gas that Forms Compounds with Fluorine

The smallest noble gas that forms compounds with Fluorine is Xenon (Xe). The symbol to fill in the blank for clue (10) is Xe.

Identify the Toxic Element that Forms Tetrameric Molecules

The toxic element that, like phosphorus and antimony, forms tetrameric molecules when uncombined with other elements is Arsenic (As). The symbol to fill in the blank for clue (11) is As.

Identify the Element in Air and Used in Fertilizers and Explosives

The element that occurs as an inert component of air but is a very prominent part of fertilizers and explosives is Nitrogen (N). The symbol to fill in the blank for clue (12) is N.

Key concepts

Halogens

Halogens are a fascinating group of elements located in Group 17 of the periodic table. These include Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). The term "halogen" means "salt-former," as these elements readily form salts when they react with metals. One of the remarkable properties of halogens is their ability to form acids with hydrogen, known as hydrogen halides. For example:

• Fluorine forms hydrofluoric acid (HF), which is unique as it is a weak acid in aqueous solution.
• Chlorine forms hydrochloric acid (HCl), a strong acid widely known for its use in digestion and industry.
• Bromine forms hydrobromic acid (HBr), which has a high boiling point in the series of HX compounds, second only to HF.

Halogens can be either gaseous like Fluorine and Chlorine, liquid like Bromine, or solid like Iodine at room temperature. They exhibit diverse physical states due to their van der Waals forces which increase with atomic size. Halogens are crucial in a variety of applications, from disinfection to industrial chemistry.

Periodic Table

The periodic table is an organized chart of chemical elements, arranged by increasing atomic number, which corresponds to the number of protons in an atom's nucleus. Elements are grouped in columns, known as "groups," based on similar properties and electron configurations. Rows are called "periods."
The periodic table is essential for understanding chemical behavior. For example:

• Group 1 elements are alkali metals, known for being highly reactive, especially with water.
• Group 17 elements, the halogens, are covered in the previous section, and are known for forming salts.
• Group 18 elements are the noble gases, characterized by their lack of reactivity.

Each element box contains crucial information, such as its atomic number, symbol, and atomic mass. Some elements, like Helium, were discovered in space (in the sun) before being found on Earth. The periodic table not only categorizes elements but also helps predict the types of chemical reactions they may undergo, providing a framework for studying chemistry.

Hydrogen Halides

Hydrogen halides are compounds formed between hydrogen and halogens, with a general formula of HX. These compounds exhibit varying properties based on the halogen they are paired with. When dissolved in water, each hydrogen halide forms a hydrohalic acid:

• HF (hydrofluoric acid) is a weak acid, differing from the stronger acids HCl, HBr, and HI due to its bond strength.
• HCl (hydrochloric acid) is commonly used in laboratories and industrial processes.
• HBr (hydrobromic acid) and HI (hydroiodic acid) are similar to HCl but have weaker bonds and higher boiling points.

These acids are important in both laboratory and industrial settings, used for applications ranging from etching glass (HF) to being a component in aqua regia, a potent acid mixture used for dissolving noble metals. The variations in acidity and boiling points among hydrogen halides arise from differing bond strengths and molecular interactions. Understanding hydrogen halides is key to grasping concepts related to acid-base chemistry and their practical applications.

Noble Gases

Noble gases form a unique group of elements located in Group 18 of the periodic table, consisting of Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). Known for their exceptional stability and low reactivity, these gases have complete outer electron shells, making them inert under normal conditions. This is why these elements were termed "noble," paralleling the aloofness attributed to nobility.
Noble gases have several fascinating aspects:

• Helium is light and stable, widely used in balloons and as a cooling medium for nuclear reactors.
• Neon is famous for its use in colorful neon signs due to its ability to emit light when electrified.
• Argon, being abundant in Earth's atmosphere, is commonly used in welding as a shielding gas.
• Xenon can form compounds with fluorine, such as \( ext{XeF}_2\) and \( ext{XeF}_4\), showcasing its ability to participate in chemical reactions despite its "noble" status.

These noble gases play crucial roles in various modern technologies and scientific research areas. Understanding their properties and applications helps appreciate the valuable contributions they make to industry and scientific advancement.