Question

How does the boiling point change across the periodic table?

Answer 1

Hint:Boiling point, melting point, density, viscosity, refractive index, etc are different physical properties of the substances.All these properties are intensive and independent of the amount of the substance.The boiling point is the temperature when liquid is converted into vapors when its vapor pressure becomes equal to the atmospheric pressure.There is an inverse relationship between the vapor pressure and the boiling point of the liquid.

Complete answer:The van der forces existing between the atoms, ions, or molecules affect the boiling point.Along with the group from top to bottom of the periodic table size of atoms increases hence, the strength of van der Waals forces also increases.As the strength of van der Waal forces increases boiling point also increases.Therefore, in general, we can say that along with the group from top to bottom boiling point increases but there is some exception to this also.Across the period from left to right of the periodic table size of atoms decreases. As the size decreases the strength of van der Waals forces also decreases. As strength decreases, the boiling point also decreases.There decreases in boiling point is observed as we move from left to right of the periodic table with some exceptions.

Note:The boiling point of the compound depends on the intermolecular forces present in the compounds.Stronger is the force of the attraction present in the particles of the compound greater is the boiling point of the compound and vice versa.If intermolecular forces increase, the vapor pressure of the compound decreases, and hence the boiling point of the compound increases.Thus, by comparing the relative strength of the intermolecular forces between the compounds we can determine the relative boiling points of the compounds.