An ionic bond between two atoms is formed when which of the following processes occurs?

Introduction / Context:
Ionic bonds are one of the basic types of chemical bonds that hold atoms together in compounds such as salts. Understanding how these bonds form is crucial for predicting properties like melting point, solubility, and electrical conductivity. This question asks you to choose the best description of the process that leads to the formation of an ionic bond between two atoms.

Given Data / Assumptions:

• We are dealing with two atoms, typically one metal and one nonmetal.
• The options describe sharing, transfer of electrons, combined processes, and losing of protons.
• We assume normal conditions and typical ionic compounds like NaCl or MgO as examples.

Concept / Approach:
An ionic bond forms when electrons are transferred from one atom, usually a metal, to another atom, usually a nonmetal. The metal atom loses electrons and becomes a positively charged cation, while the nonmetal atom gains electrons and becomes a negatively charged anion. The electrostatic attraction between these oppositely charged ions constitutes the ionic bond. Therefore, the correct description must emphasize electron transfer and the formation of ions that attract each other, not sharing of electrons or changes in protons.

Step-by-Step Solution:
Step 1: Recall that metals have a tendency to lose valence electrons, forming positive ions. Step 2: Recall that nonmetals tend to gain electrons to complete their valence shells, forming negative ions. Step 3: Consider a typical example, such as sodium and chlorine forming NaCl. Sodium transfers one valence electron to chlorine. Step 4: After transfer, Na becomes Na plus and Cl becomes Cl minus, and a strong electrostatic attraction arises between them. Step 5: Identify the option that explicitly describes this process of electron transfer and ion formation leading to ionic bonding.

Verification / Alternative check:
Electron configuration provides an alternative check. For sodium, losing one electron gives a stable noble gas configuration, and for chlorine, gaining one electron also results in a stable configuration. The formation of Na plus and Cl minus ions thus lowers the energy of the system and creates a stable ionic lattice. In contrast, sharing electrons as in covalent bonding leads to different structures and properties. This reasoning confirms that electron transfer and ionic attraction are central to ionic bond formation.

Why Other Options Are Wrong:
Option A, sharing of electrons, describes covalent bonding rather than ionic bonding. Option C, both sharing and transfer at the same time, mixes concepts and does not correspond to a standard bond type in simple compounds. Option D, losing of protons from the nucleus, would change the element itself and is not how chemical bonds form, since proton number defines the element. Only option B correctly captures the essence of ionic bond formation: transfer of electrons from a metal atom to a nonmetal atom and the resulting electrostatic attraction between ions.

Common Pitfalls:
Students may confuse the terms because ionic and covalent bonds both lead to stable compounds and involve valence electrons. Another pitfall is overlooking the role of charge attraction and focusing only on electron movement without connecting it to the formation of ions. To avoid these errors, remember that ionic bonds are always associated with electron transfer and ion formation, while covalent bonds are associated with electron sharing between atoms. Keeping these definitions clear makes questions about bond types much easier to answer.

Final Answer:
An ionic bond is formed when there is transfer of electrons from a metal atom to a nonmetal atom, producing oppositely charged ions that attract each other.