Answer the question on the basis of passage given below:
Second period elements of p-Block differ from the rest of their group members due to their small atomic size, high electronegativity, high ionization enthalpy and absence of d-orbitals.
The elements from the second period like C, N, O have unique property of forming pπ–pπ multiple bonds whereas other heavier elements of p-block form dπ–pπ multiple bonds. This changes the properties of second period elements to great extent. Also the single bond strength of the p-block elements with their own atoms gets affected by their atomic size and presence of lone pairs.
Inert pair effect also affects the properties of the p-Block elements especially for those elements which are present from 4th period onward and this happens due to poor screening effect of inner (n–1)d subshell electrons.
The decreasing order of melting point of the following elements will be:-
A. Nitrogen (N)
B. Phosphorus (P)
C. Arsenic (As)
D. Antimony (Sb)
E. Bismuth (Bi)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → As > Sb > Bi > P > N
Down group 15 the melting point increases up to arsenic and then decreases up to bismuth. Nitrogen and phosphorus are made of small molecules held by weak forces; arsenic, antimony and bismuth have extended structures, in which the bonding weakens from As to Bi as the atoms become larger.
A. Nitrogen — fifth (last), 63 K. It is a gas of small \( \ce{N2} \) molecules held only by weak van der Waals forces.
B. Phosphorus — fourth, 317 K (white phosphorus). Its \( \ce{P4} \) molecules are larger than \( \ce{N2} \) but are still discrete molecules.
C. Arsenic — first, 1089 K. It has the highest melting point of the group, where the trend turns.
D. Antimony — second, 904 K. The atoms are larger than arsenic, so the bonding is weaker.
E. Bismuth — third, 544 K. It is the largest atom and forms weak metallic bonds.
NCERT (Pre-rationalised edition, 2022-23):
Physical Properties
