5.13 Metallic Bond

1. Formation of Metallic Bond:

• A metallic bond occurs when two metallic elements come close together, forming a bond due to the attraction between metal atoms.

• In a piece of metal, numerous atoms of the same element are interconnected through metallic bonds, such as copper wire, scissors, gold ornaments, etc.

• The outermost energy level of metallic atoms typically contains 1, 2, or 3 electrons. These electrons are less tightly held due to the larger size of metallic atoms compared to non-metallic atoms in the same period.

• As a result, these outermost electrons are donated by the metal atoms, turning them into positively charged ions, called atomic cores.

• These atomic cores are arranged in a three-dimensional lattice in the metal.

2. Delocalized Electrons:

• The electrons donated by the metal atoms do not stay with individual atoms. Instead, they become delocalized electrons that move freely throughout the metal lattice.

• These delocalized electrons create a “sea of electrons” around the atomic cores. This movement of electrons is what forms the metallic bond, as the electrons are attracted to the positively charged ions through electrostatic forces.

• These delocalized electrons are responsible for key properties of metals, including:

• Electrical conductivity: Delocalized electrons can move freely, allowing metals to conduct electricity.

• Heat conductivity: The electrons can transfer energy quickly, enabling metals to conduct heat.

• Flexibility: The structure of the metallic bond allows metal atoms to slide past each other, making metals flexible.

• Brightness: The free-moving electrons reflect light, giving metals their shiny appearance.

• Charge resistance: Delocalized electrons can resist changes in charge, adding stability to the metal.

3. Electrical Conductivity of Metals:

• Metals are good conductors of electricity due to the presence of delocalized electrons.

• When a metal is connected to a battery, the delocalized electrons move from the negative terminal to the positive terminal, allowing electricity to flow through the metal.

• The flow of electrons is what constitutes the flow of electricity.

4. Heat Conductivity of Metals:

• Metals are also good conductors of heat because of the delocalized electrons.

• When heat is applied to one end of a metal, the electrons gain energy and increase their velocity. These fast-moving electrons transfer energy from the hot end to the cooler end, thus conducting heat through the metal.

5. Experiment - Identifying Ionic and Covalent Compounds:

• To identify ionic and covalent compounds, you can perform the following experiment:

• Take edible salt, kerosene, naphthalene, washing soda, etc., and place them in separate beakers with water.

• Stir each mixture and observe which substances dissolve in water:

• Ionic compounds, like edible salt and washing soda, will dissolve in water.

• Covalent compounds, like kerosene and naphthalene, will not dissolve in water.

• This process helps to categorize compounds as either ionic or covalent based on their solubility in water.

This section explains the metallic bond and highlights the unique properties of metals due to the presence of delocalized electrons, such as electrical and heat conductivity, flexibility, and brightness.