Question

Choose the correct option that does not describe the property of a metallic solid:
i) Metallic solids are good conductors of electricity.
ii) There are metallic bonds present in these atoms that are holding them together.
iii) Metallic solids can have high melting points.
iv) Metallic solid is not a subcategory of crystalline solid.

Answer 1

Solids in which atoms, ions and molecules are arranged in a definite and repeating three-dimensional pattern forming a crystal lattice which extends in all directions are known as crystalline solids. These can be further classified into four types i.e., ionic solids, molecular solids, covalent-network solids and metallic solids.

Complete answer:
Metallic solids: The solids which are made up of metal atoms held together by metallic bonds. These are characterized by high melting points and can range from soft and malleable to very hard solids. Now, let us check each given property of metallic solid separately.
Property-1: Metallic solids are good conductors of electricity-
Metals are an orderly collection of positive ions which are surrounded and held together by a sea of electrons. These electrons are mobile and are evenly spread throughout the crystal lattice. These free and mobile electrons are responsible for high thermal and electrical conductivities of metallic solids. Thus, metallic solids are good conductors of electricity.
Property-2: There are metallic bonds present in these atoms that are holding them together-
In metals, atoms readily lose electrons in order to form positive ions i.e., cations and these ions are surrounded by delocalized electrons. The solid is held together by electrostatic interactions acting between the ions and the electron cloud and these interactions are referred to as metallic bonds. Thus, there exist metallic bonds which hold the atoms of metallic solids together.
Property-3: Metallic solids can have high melting points-
Due to strong metallic bonds between the atoms of metallic solids, they possess very high melting and boiling points.
Property-4: Metallic solid is not a subcategory of crystalline solid-
It is not a property of metallic solid because we know that metal cations in metallic solids are surrounded by clouds of electrons in a fixed lattice and thus, it is a type of crystalline solid.
Hence, option (iv) is the correct answer.

Note:
It is important to note that the metallic bond for a metallic bond is always nondirectional because electrons are not shared with a particular atom in one direction. However, the electrons are shared with many neighbouring atoms in different directions.