In which of the following groups of substances would dispersion forces be the only significant factors in determining boiling points? I. Cl2II. HFIII. NeIV. KNO2V. CCl4

Cl2, Ne, CCl4 are the group of substances in which dispersion forces would

help determine the boiling point.

Dispersion force  is a type of Van der waals force and is also regarded as

London forces. This type of force occur between the atoms and molecules

when electrons are symmetrically distributed in the nucleus.

This force is a weak intermolecular force and is present in non polar

compounds such as Cl2, Ne, CCl4 . KNO2 is polar and hence doesn't

determine its boiling point.

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Cl2,Ne, CCl4

Explanation:

Dispersion forces are quite significant as the predominant intermolecular forces in nonpolar substances. For Cl2,Ne and CCl4, dispersion forces are the primary kind of intermolecular interaction present in the compound.

Hence, the boiling point of these substances will be determined solely by the dispersion forces between the molecules.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.