Embibe Experts Solutions for Chapter: Classification of Elements and Periodicity in Properties, Exercise 3: Exercise 3

Assertion: Caesium is the most electropositive element in the periodic table.
Reason: Caesium has the lowest first ionisation energy among all the elements.

Assertion : Electron affinity values of the $3^{\mathrm{rd}}$ period elements on extreme right of the periodic table except noble gases are generally more than the $2^{\mathrm{nd}}$ period element of the same group.
Reason : Due to smaller atomic size of the $2^{\mathrm{nd}}$ period element, its electron density increases which oppose the addition of electron.

Assertion: Nitrogen (atomic number $7$) has less electron affinity than the oxygen (atomic number $8$).
Reason: The magnitude of an element's electron affinity only depends on the element's valence shell electrons configuration.

Assertion: Second electron gain enthalpy of halogens is always positive.
Reason: Fluorine has maximum value of electron gain enthalpy.

Assertion : The atomic radii of the elements of the oxygen family are smaller than the atomic radii of the corresponding elements of the nitrogen family.
Reason : The members of the oxygen family are more electronegative and thus have lower values of nuclear charge than those of the nitrogen family.

Assertion: Fluorine has a less negative electron gain enthalpy than chlorine.
Reason: There is relative greater effectiveness of $2\mathrm{p}-$electrons in the small $\mathrm{F}$ atom to repel the additional electron entering the atom than to $3\mathrm{p}-$electrons in the larger $\mathrm{Cl}$ atom.

Assertion: $\mathrm{Li}$ and $\mathrm{Mg}$ shows diagonal relationship.
Reason: $\mathrm{Li}$ and $\mathrm{Mg}$ are diagonal to each other in the periodic table