Could you give an explanation of each answer? correct answer. a. to the \"electr

Question

Could you give an explanation of each answer?

correct answer. a. to the "electron-sea" model of metal-metal bonding, which element should be harder; V or Zn? b. According to the molecular orbital band" model of metal-metal bonding, which element should have higher melting point; Cu or Cr? e. Which of the metal-metal bonding models listed above in a. and b. gives a more accurate prediction of metallic properties; MO band or "electron-sea"? d. According to the band theory, decreasing melting points in metals is due to the filling of which type of molecular orbitals; bonding or antibonding? e. For a nonmetal ergy gap between the bonding Mo band and the antibonding MO band is; very large or very small? f For a semiconductor, the energy gap between the bonding and antibonding Mo bands is; small or medium or large? g. Which compound should be a semiconductor? (50/50 molar mixtures for beth) Zn/Te or Ga/See 2. For a material to be a semiconductor, how many electrons (on average per atom are required to fill the bonding Mo band: 1,2, 3, 4, 5, 6, 7, er 8?

Explanation / Answer

(a) According to electron sea model strength of metallic bond increases with increased number of electron. In Zn number of electrons is more and as a result, it will have a atronger inter metallic attraction which makes it stronger than V.

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(b) In Molecular orbital description of transition metal , there are two types of interaction : metal-metal interaction through bonding orbitals , metal-metal interaction through anti bonding orbitals. Interaction through bonding orbitals are stronger than the one involved anti bonding interaction and as a result , greater melting point.

Cr forms metallic bonding through bonding orbital. hence it has stronger metallic bonding and greater melting point.

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(c) The electron-sea model, however, does not adequately explain all properties. For example, according to the model, the strength of bonding between metal atoms should increase as the number of valence electrons increases, resulting in a corresponding increase in melting points. However, the group 6B metals (Cr, Mo, W), which are in the center of the transition metals, have the highest melting points in their respective periods. The melting points on either side of the center are lower , which implies that the strength of metallic bonding first increases with increasing number of electrons and then decreases. Similar trends are seen in other physical properties of the metals, such as the heat of fusion, hardness, and boiling point.

So, MO theory is better to explain metallic property.

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(d) Greater the number of electron in anti bonding orbitals, weaker is the bond and lesser is the melting point.

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(e) Metals are good conductor of electricity due to the presence of closely spaced valence band and conduction band. This gap is large in non-metal. Thats why ther are insulator.

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