International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What best describes the structure of metals?

1. A regular arrangement of isolated atoms

2. A giant arrangement of positive ions in a crystal lattice

3. A giant regular structure of positive ions surrounded by delocalised electrons

4. A simple covalent structure

The correct answer is: A giant regular structure of positive ions surrounded by delocalised electrons

The structure of metals is best described as a giant regular structure of positive ions surrounded by delocalised electrons. This definition captures the essence of metallic bonding, where the metal atoms lose some of their electrons, allowing them to move freely throughout the structure. This flow of delocalised electrons is responsible for many of the properties we associate with metals, such as electrical conductivity and malleability. In this structure, the positive ions form a closely packed arrangement, creating a strong electrostatic attraction between the positively charged metal ions and the negatively charged, delocalised electrons. This arrangement leads to the characteristic strength and ductility of metals. Furthermore, the regular arrangement of ions contributes to the overall stability of the metal's crystal lattice. The other choices do not accurately represent this unique structure. For instance, the idea of isolated atoms would suggest a non-metallic or covalent bonding structure, which does not apply to metals. Similarly, while the presence of positive ions in a crystal lattice is part of the description, it lacks the important detail of delocalised electrons essential to metallic bonding. Lastly, a simple covalent structure pertains to non-metals and does not depict the extensive and strong interactions found within metals.