Which one of the following bonds produces a solid that reflects light in the visible region and whose electric

Question

Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has a high melting point?

Accepted Answer

1. **Metallic Luster (Reflects Light):** Metals have a unique luster and reflect light due to the presence of free, mobile electrons (sea of electrons) that interact with incident light.
2. **Electrical Conductivity vs Temperature:** Metals are excellent conductors due to these free electrons. However, **metallic (electronic) conductance decreases with an increase in temperature** [Class 12 Chemistry, Unit 2, Sec 2.4.1]. This occurs because increasing temperature increases the thermal vibration of the positive metal kernels, which hinders the flow of electrons.
3. **High Melting Point:** Strong metallic bonding (electrostatic attraction between positive kernels and the electron sea) generally results in high melting points [Class 12 Chemistry, Unit 4, Sec 4.3.1].
4. **Comparison:** Ionic solids are insulators in the solid state. Covalent network solids (like diamond) have high melting points but are insulators. Molecular solids (Van der Waals) have low melting points.

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