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

• metallic bonding

• van der Waal's bonding

• Ionic bonding

• Ionic bonding

2.

If the lattice parameter for a crystalline structure is 3.6 A, then atomic radius in fcc crystal is

• 1.18 A

• 2.10 A

• 2.92 A

• 2.92 A

Assertion:  Unlike electric force and gravitational forces, nuclear force has limited range.

Reason:  Nuclear force do not obey inverse square law.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  The Coulomb force is dominating force in the universe. 

Reason: The Coulomb force is weaker than the gravitational force.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

The force of gravitation is

• repulsive

• conservative

• electrostatic

• non-conservative