Two or more forms of an element with different bonding structure in the same physical phase are called

• A. Isotopes
• B. Isomers
• C. Allotropes
• D. Compounds

Answer: (C)

Allotropy is when an element can exist in two or more forms with different bonding structures in the same physical phase. For example, carbon appears as diamond, with a rigid 3D network of strong covalent bonds, and as graphite, with layered sheets of carbon atoms bonded differently and held together by weaker forces between layers. Oxygen also has two forms in the same phase: O2 and O3, which differ in how the atoms are bonded. These distinct forms of the same element are called allotropes. Isotopes are versions of an element with different numbers of neutrons (mass changes but bonding stays the same), isomers involve different arrangements of atoms within different molecules, and compounds are substances made from two or more elements. Allotropes specifically refer to different bonding arrangements of the same element in the same phase.