Question

Which of the following statements 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

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

Step-by-step solution

Checking the Truthfulness of Statement a

Most of the known elements are metals. This statement is true. The majority of the elements found in the periodic table are classified as metals. Metals are usually found on the left side and in the middle of the periodic table.

Checking the Truthfulness of Statement b

Element 118 should be a nonmetal. This statement is false. Element 118 belongs to the Group 18 elements, which are known as noble gases, and it is called Oganesson (Og). Noble gases are classified as nonmetals, but they are in a separate category due to their unique properties and low reactivity. Therefore, we can correct the statement to: "Element 118 should be a noble gas."

Checking the Truthfulness of Statement c

Hydrogen has mostly metallic properties. This statement is false. Though hydrogen is placed above the alkali metals in the periodic table, it does not exhibit metallic properties. Instead, it possesses the properties of nonmetals and is classified as a nonmetal. Hydrogen is a gas at room temperature, does not conduct electricity, and has a low melting and boiling point compared to metals.

Checking the Truthfulness of Statement d

A family of elements is also known as a period of elements. This statement is false. A family of elements is a group of elements with similar properties, located in the same vertical column of the periodic table. These are also called groups. In contrast, a period is a horizontal row in the periodic table, and the elements in a period differ in properties. We can correct the statement to: "A family of elements is also known as a group of elements."

Checking the Truthfulness of 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. First, the compound formed between an alkali earth metal and a halogen is primarily ionic, not covalent. Secondly, the formula is incorrect. Alkaline earth metals, such as magnesium or calcium, are in Group 2 of the periodic table and have a +2 charge when forming an ionic compound. Halogens, such as fluorine or chlorine, are in Group 17 and have a -1 charge. The ionic compound formed between an alkaline earth metal, A, and a halogen, X, will have the formula AX₂, due to the need to balance the charges. We can correct the statement to: "When an alkaline earth metal, A, reacts with a halogen, X, the formula of the ionic compound formed should be \(\mathrm{AX}_{2}\)."

Key concepts

Classification of Elements

Elements on the periodic table are organized based on their atomic number, electron configurations, and recurring chemical properties, primarily into metals, nonmetals, and metalloids. Metals, which make up the majority of elements, are typically found on the left side and in the middle of the periodic table. They are known for being good conductors of heat and electricity, having a shiny luster, being ductile and malleable, and often having higher densities and melting points.

Nonmetals, on the other hand, are located on the upper right side of the periodic table. They are poor conductors of heat and electricity, and they often have lower densities and melting points than metals. The nonmetals include the halogens and noble gases, with noble gases like Element 118 (Oganesson) being distinct for their low reactivity due to a full valence electron shell. Metalloids have intermediate properties and serve as a bridge between metals and nonmetals on the periodic table.

Chemical Bonding

Chemical bonding is the process by which atoms combine to form compounds. There are three primary types of chemical bonds: ionic, covalent, and metallic. Ionic bonding occurs between metals and nonmetals, where electrons are transferred from one atom to another, resulting in a lattice of positively and negatively charged ions. In covalent bonding, typically between nonmetals, atoms share electron pairs.

Metallic bonding, characteristic of metals, involves a 'sea' of delocalized electrons around a lattice of positively charged metal ions. This delocalization results in the high conductivity and malleability of metals. Understanding these bonding types is fundamental in predicting compound formation and behavior.

Ionic and Covalent Compounds

Ionic and covalent compounds differ significantly in their properties and formation. Ionic compounds form from the electrostatic attraction between oppositely charged ions, typically a metal cation and a nonmetal anion. Their structure is a crystal lattice which endows them with high melting and boiling points, and they often dissolve in water to form electrolytes.

Covalent compounds are formed by atoms that share electrons in pairs, usually between nonmetals. These compounds can exist as gases, liquids, or solids at room temperature and tend to have lower boiling and melting points than ionic compounds. They do not conduct electricity as solids but can do so if dissolved in water depending on their polarity.

Metallic and Nonmetallic Properties

Metallic and nonmetallic properties determine the reactivity and use of elements and their compounds. Metals typically have a shiny appearance, are heavy and dense, can be shaped (malleability), and drawn into wires (ductility). They tend to lose electrons during chemical reactions, forming positive ions.

Nonmetals have a more varied appearance, including gases like hydrogen, liquids like bromine, and solids like sulfur. They tend to gain or share electrons when reacting, often forming negative ions or covalent bonds. The variations in these properties across the periodic table enable a vast array of chemical reactions and compounds.