Question

Which of the following statements is true? (A) Hydrogen bonds to itself, forming hydrogen bonds. (B) Carbon reacts with hydrogen by sharing valence electrons to form covalent bonds. (C) Potassium reacts with chlorine by sharing valence electrons to form a covalent bond. (D) Magnesium reacts with argon to form ionic bonds.

Short answer

The correct statement is (B): Carbon reacts with hydrogen by sharing valence electrons to form covalent bonds.

Step-by-step solution

Statement A: Hydrogen bonds to itself, forming hydrogen bonds.

Statement A is false. Hydrogen can bond to itself, but it forms a covalent bond (not hydrogen bond). Hydrogen bonds are a type of intermolecular force that occurs between a hydrogen atom and a more electronegative atom, such as oxygen, nitrogen, or fluorine.

Statement B: Carbon reacts with hydrogen by sharing valence electrons to form covalent bonds.

Statement B is true. Carbon (C) and hydrogen (H) form covalent bonds by sharing valence electrons. This is a common type of bond, which can be found in many organic molecules, such as methane (CH4).

Statement C: Potassium reacts with chlorine by sharing valence electrons to form a covalent bond.

Statement C is false. Potassium (K) reacts with chlorine (Cl) to form an ionic bond, not a covalent bond. Potassium, a metal, donates its one valence electron to the nonmetal chlorine, which needs one electron to complete its valence shell. This results in potassium becoming a positively charged ion (K+) and chlorine becoming a negatively charged ion (Cl-). The attraction between these ions forms an ionic bond, creating the compound potassium chloride (KCl).

Statement D: Magnesium reacts with argon to form ionic bonds.

Statement D is false. Magnesium (Mg) cannot form an ionic bond with argon (Ar). This is because argon is a noble gas, and it has a full valence shell of electrons, making it stable and unreactive. As a result, argon does not form chemical bonds with other elements, such as magnesium. In conclusion, the true statement is: (B) Carbon reacts with hydrogen by sharing valence electrons to form covalent bonds.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom's electron shell and play a crucial role in chemical bonding. These electrons determine how an element will interact and bond with other elements. When atoms come together to form compounds, it is the valence electrons that are involved in this process.
Atoms tend to achieve a stable electron configuration, often resembling that of the nearest noble gas. This stability is frequently achieved through the sharing or transferring of valence electrons.

• Sharing of Electrons: In a covalent bond, atoms share their valence electrons to achieve stability. For example, carbon and hydrogen share electrons to form methane ( ext{CH}_4), each contributing to the other's stability.
• Transfer of Electrons: Ionic bonds involve the transfer of valence electrons from one atom to another, resulting in the formation of ions. One atom becomes positively charged (cation) while the other becomes negatively charged (anion).

Elemental Reactions

Elemental reactions refer to the ways in which elements react with each other to form new substances. The nature of these reactions is primarily determined by the behavior of an element's valence electrons.

• Covalent Bonding: This type of bonding occurs when two nonmetals, such as carbon and hydrogen, share valence electrons. Covalent bonds are very common in organic molecules and contribute to the formation of complex structures like proteins and nucleic acids.
• Ionic Bonding: Ionic bonds form between metals and nonmetals, such as potassium and chlorine. Here, electrons are transferred from one atom to another, resulting in oppositely charged ions that are held together by electrostatic forces.

Reactions between elements are the basis of chemical synthesis and are essential for creating the myriad of compounds that exist in nature.

Organic Molecules

Organic molecules are primarily composed of carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements. The versatility of carbon atoms in forming covalent bonds makes organic molecules remarkably diverse and complex.

• Structure of Organic Molecules: Organic molecules often contain chains or rings of carbon atoms bonded to hydrogens and other atoms. This ability to form long chains and complex structures leads to a vast array of molecule types.
• Covalent Bonds in Organic Molecules: These molecules rely heavily on covalent bonds. The sharing of valence electrons allows for the formation of stable structures that are integral to life, such as DNA and proteins.

The study of organic molecules is a fundamental aspect of chemistry and biochemistry because they form the basis of life on Earth. Their ability to form a wide variety of bonds and structures enables the existence of the diverse biological processes necessary for life.