Concept: Electrovalent (Ionic) Compounds

Electrovalent compounds, also known as ionic compounds, are formed by the complete transfer of one or more electrons from a metal atom to a non-metal atom. This transfer results in the formation of positively charged ions (cations) and negatively charged ions (anions). These oppositely charged ions are held together by strong electrostatic forces of attraction, forming a crystal lattice.

Why (C) is correct:

In an electrovalent compound, the fundamental building blocks are not neutral atoms or molecules, but rather charged species called ions. These ions arrange themselves in a highly ordered, three-dimensional structure known as a crystal lattice, where each ion is surrounded by ions of opposite charge. For example, in NaCl, Na⁺ ions and Cl^- ions are arranged in a crystal lattice.

Option Analysis:

• A) atoms: Atoms are the building blocks of elements and covalent compounds, but not typically the primary components of an ionic crystal lattice. While the ions originate from atoms, they exist as charged species in the lattice.
• B) molecules: Molecules are formed by covalent bonding (sharing of electrons) and are characteristic of molecular compounds, not electrovalent (ionic) compounds. Ionic compounds do not exist as discrete molecules in the solid state.
• D) both molecules and ions: This option is incorrect because electrovalent compounds are composed solely of ions, not a combination of molecules and ions.

Correct Answer: (C)