Tungsten is hard and has a very high melting point (3422 °C), and gold is soft and has a relatively low melting point (1064 °C). Are these facts in better agreement with the electron-sea model or the MO model (band theory)? Explain.

Verified step by step guidance

1. Step 1: Understand the electron-sea model and the MO model (band theory). The electron-sea model suggests that metal atoms release some of their electrons to form a 'sea' of electrons that are free to move throughout the metal lattice, which explains properties like electrical conductivity and malleability. The MO model (band theory) explains the bonding in metals by considering the overlap of atomic orbitals to form molecular orbitals, which are spread out over the entire metal lattice, creating energy bands.
2. Step 2: Compare the properties of tungsten and gold. Tungsten is hard and has a very high melting point (3422 °C), while gold is soft and has a relatively low melting point (1064 °C).
3. Step 3: Analyze the data in the provided table. The table shows the Mohs hardness values for various metals, indicating their relative hardness. Tungsten is not listed, but it is known to be very hard, similar to chromium (Cr) with a Mohs hardness of 8.5. Gold, on the other hand, is softer than copper (Cu) with a Mohs hardness of 3.
4. Step 4: Relate the properties of tungsten and gold to the electron-sea model and the MO model. The electron-sea model does not adequately explain the differences in hardness and melting points between tungsten and gold. The MO model (band theory) can better explain these differences by considering the different extents of orbital overlap and the resulting energy band structures in these metals.
5. Step 5: Conclude that the facts about tungsten and gold are in better agreement with the MO model (band theory) because it provides a more detailed explanation of the differences in their physical properties, such as hardness and melting points, based on their electronic structures.

Key Concepts

Electron-Sea Model

The electron-sea model describes metals as a lattice of positive ions surrounded by a 'sea' of delocalized electrons. This model explains many properties of metals, such as electrical conductivity and malleability, as the free-moving electrons can easily respond to applied forces. The strength of metallic bonds in this model is influenced by the number of delocalized electrons, which contributes to hardness and melting points.

Molecular Orbital (MO) Theory

Molecular Orbital (MO) theory, or band theory in the context of metals, describes how atomic orbitals combine to form molecular orbitals that can be occupied by electrons. In metals, these orbitals form bands that allow for the conduction of electricity. The energy gap between the valence band and the conduction band determines the electrical and thermal properties of the metal, influencing characteristics like hardness and melting point.

Melting Point and Hardness Correlation

The melting point and hardness of a metal are often correlated with its bonding characteristics. Metals with strong metallic bonds, such as tungsten, typically exhibit high melting points and hardness due to the strong attraction between the delocalized electrons and the metal ions. In contrast, metals with weaker bonding, like gold, tend to be softer and have lower melting points, reflecting the differences in their electronic structures and bonding interactions.