Question

Which of the following statements is(are) true? For the false statements, correct them. a. Most of the known elements are metals. b. Element 118 should be a nonmetal. c. Hydrogen has mostly metallic properties. d. A family of elements is also known as a period of elements e. When an alkaline earth metal, A, reacts with a halogen, X, the formula of the covalent compound formed should be \(\mathrm{A}_{2} \mathrm{X}\) .

Short answer

True statements: a. Most of the known elements are metals. b. Element 118 should be a nonmetal. False statements with corrections: c. Hydrogen has mostly nonmetallic properties. d. A family of elements is also known as a group of elements. e. When an alkaline earth metal, A, reacts with a halogen, X, the formula of the ionic compound formed should be \(\mathrm{A}\mathrm{X}_{2}\).

Step-by-step solution

Statement a: Most of the known elements are metals.

This statement is true. Most of the elements in the periodic table are classified as metals, and they are found on the left side and middle of the table.

Statement b: Element 118 should be a nonmetal.

Element 118 is Oganesson (Og), which belongs to the Group 18 of the periodic table, also known as Noble gases. The elements in this group are generally nonmetals due to their full electron shells, making them inert and unreactive. So, this statement is true.

Statement c: Hydrogen has mostly metallic properties.

This statement is false. Hydrogen is actually a nonmetal and belongs to Group 1 of the periodic table (the alkali metals). However, it is unique and has some properties that are different from other alkali metals, such as being a gas at room temperature and forming diatomic molecules (H2). Hydrogen does not possess metallic properties, as it forms covalent bonds instead of metallic bonds. Corrected statement: Hydrogen has mostly nonmetallic properties.

Statement d: A family of elements is also known as a period of elements.

This statement is false. A family (or group) of elements is a vertical column in the periodic table, whereas a period is a horizontal row of elements. Families of elements share similar chemical properties, whereas elements in the same period have varying properties. Corrected statement: A family of elements is also known as a group of elements.

Statement e: When an alkaline earth metal, A, reacts with a halogen, X, the formula of the covalent compound formed should be \(\mathrm{A}_{2} \mathrm{X}\).

This statement is false. Alkaline earth metals are in Group 2 of the periodic table. They lose two electrons to form a +2 charge when reacting with other elements. Halogens are in Group 17 and form a -1 charge by gaining one electron. The correct formula for a compound formed between an alkaline earth metal (A) and a halogen (X) is \(\mathrm{A}\mathrm{X}_{2}\). Also, the compound formed is an ionic compound, not a covalent compound. Corrected statement: When an alkaline earth metal, A, reacts with a halogen, X, the formula of the ionic compound formed should be \(\mathrm{A}\mathrm{X}_{2}\).

Key concepts

Metals

Metals are a significant category of elements in the periodic table. They are known for their conductivity, malleability, and lustrous appearance. Most metals are found on the left side and center of the periodic table. These elements have properties such as:

• Good electrical and thermal conductivity, due to the free movement of electrons.
• Malleability and ductility, allowing them to be shaped and stretched into wires.
• A shiny, metallic luster that reflects light.

Metals tend to lose electrons when forming chemical bonds, resulting in positive ions. This characteristic is crucial in forming ionic compounds where metals typically donate electrons to nonmetals.

Nonmetals

Nonmetals are found primarily on the right side of the periodic table. They display a wide range of properties distinct from metals, including:

• Poor conductivity of heat and electricity; they are insulators.
• Brittle nature in the solid state, meaning they break rather than deform.
• Dull appearance, lacking the shine seen in metals.

Nonmetals frequently gain electrons when participating in chemical reactions, forming negative ions. This tendency plays a crucial role in creating ionic compounds. Additionally, nonmetals such as hydrogen can form covalent bonds by sharing electrons.

Alkaline Earth Metals

Alkaline earth metals are located in Group 2 of the periodic table. These elements, including calcium and magnesium, have properties that are characterized by their high melting points and reactivity. Key features include:

• They have two electrons in their outer shell, making them eager to lose both to form ions with a +2 charge.
• They are less reactive than alkali metals but react readily with halogens, forming ionic compounds.
• These metals contribute to important biological processes, highlighting their significance beyond just chemical properties.

Alkaline earth metals form compounds like oxides and sulfates and are typically found in mineral deposits.

Halogens

Belonging to Group 17 in the periodic table, halogens are unique nonmetals. This group includes fluorine, chlorine, bromine, iodine, and astatine. They are known for the following characteristics:

• High reactivity, especially with alkaline metals and alkaline earth metals, forming ionic compounds.
• Existence in diatomic forms (e.g., F₂, Cl₂) in their natural state.
• Application in various industries, such as disinfection and pharmaceuticals.

Halogens gain one electron to achieve a stable electronic configuration, resulting in ions with a -1 charge. This property makes them a perfect match for reacting with metals to form salts.

Ionic and Covalent Compounds

Chemical bonding is a fundamental concept to understand ionic and covalent compounds. These compounds differ in their formation and properties:

• Ionic Compounds: Formed when metals donate electrons to nonmetals. The resulting oppositely charged ions attract each other. For example, sodium chloride ( acl ) represents a straightforward ionic bond.
• Covalent Compounds: Result from the sharing of electrons between nonmetals. This sharing allows both atoms to achieve a stable electronic arrangement, like in water (H₂O).

Ionic compounds typically have high melting points and are good conductors of electricity when molten or dissolved in water. In contrast, covalent compounds generally have lower melting points and may not conduct electricity in any state.