Chemistry NCERT Exemplar Solutions Class 11th Chapter Three

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (iii)

Gadolinium is a lanthanoid which belongs to the f-block elements with electronic configuration (n-2)f¹⁴ (n-1)d⁰-¹ns²

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (i)

As Mg contains fully filled 3s orbital thus its ionisation is higher than that of Na and Al.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (i)

The orbitals nearer to the nucleus possess more shielding effect.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (iv)

Actinoids possess Z=90-103

Terbium is lanthanoid.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Option (ii)

All the given ions are isoelectronic species thus their radii depend upon the charge more the negative charge higher would be the atomic radii and higher the positive charge lesser would be the atomic radii.

This is a Short Answer Type Questions as classified in NCERT Exemplar

The electronegativity of the alkali metals decreases down the group due to the increase of the shells thus Cs (Caesium) is the least electronegative metal in the alkali metals.

This is a Short Answer Type Questions as classified in NCERT Exemplar

The radius of Na⁺ ion is smaller than that of Na is due to the following reasons:-

(i) The effective nuclear charge of Na⁺

(ii) The disappearance of 3s orbital from its outermost shell electronic configuration.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Metallic character- Tendency to lose electrons.

Non-Metallic character- Tendency to accept electrons.

Across the period the metallic character decreases whereas non-metallic character increases across the period.

This is a Short Answer Type Questions as classified in NCERT Exemplar

(a) As the effective nuclear charge increases and shielding effect decreases across the periods thus the electronegativity increases on moving from left to right in the periodic table.

(b) As the number of shells increases down the group thus its ionisation enthalpy decreases down the group.

The deviation in the ionization enthalpy of some elements from the general trend can be explained by the points as given below:-

(i) The fully filled and half filled orbital provide extra stability due to the symmetry

(ii) The effective nuclear charge

(iii) The e^- - e^- repulsion which lead to instability