Just want to check my answers: 1. A cubic closest-packed structure has the third

Question

Just want to check my answers:

1. A cubic closest-packed structure has the third layer of atoms sitting over the uncovered holes of the first layer of atoms?

True/False

2. The coordination number for a simple cubic structure is:

3. When there is no energy gap between the conduction band and the valence band, the substance is most likely a:

4. Substance A forms dipole-dipole attractions, substance B form dipersion forces. Which will have a higher boiling point?

5. A substance has melting point of 14.0oC. At 10oC the substance will be in:

Thanks!!

Explanation / Answer

1) the third layer can sit over the uncovered holes in the first – called an ABC pattern -------true

2) The simple cubic has a coordination number of 6 and contains 1 atom per unit cell ------ A

3) When there is no energy gap between the conduction band and the valence band, the substance is -------C (conductor)

4) Intermolecular Forces: The forces of attraction/repulsion between molecules.

Ex: Dipole-Dipole Forces, Hydrogen Bonding, London Dispersion Forces

the order of decreasing strength of inter and intra molecular forces is given by

Hydrogen-Bonding > Dipole-Dipole > London Dispersion

Liquids with high intermolecular forces need more energy to overcome these attractions. The temperature must be higher. They have higher boiling points.

answer is B) substance A

5) melting point is the temperature at which a given solid will melt answer is C) solid state

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