Questions

Sodium chloride:

The solubility rules tell you that all halides are soluble with the exception of those formed with siver, mercury, and lead ions. Since this is not the case here, sodium chloride will be soluble.

Silver nitrate:

It is soluble because all nitrates are soluble, without exception.

Potassium sulfate:

It is soluble because all sulfates are soluble with the exception of those formed with silver, calcium, barium, mercury, lead, and strontium ions.

Copper (II) hydroxyde:

It is insoluble because all hydroxides are insoluble with the exception of those formed with alkali metal ions and barium.

The Aufbau Principle states that in the ground state of an atom, an electron enters the orbital with lowest energy first and subsequent electrons are fed in the order of increasing energies.

Mark Fields

It is to overcome this opposite frictional force , that  we have to apply the needed force to make the body move