Match List I with List II and select the answer using the code given below the Lists: List I (Element) A. Phosphorus B. Nitrogen C. Neon D. Sulphur List II (Atomicity) 1. 2 2. 1 3. 8 4. 4 Code:
- (a)A-4, B-1, C-2, D-3
- (b)A-4, B-2, C-1, D-3
- (c)A-3, B-2, C-1, D-4
- (d)A-3, B-1, C-2, D-4
Answer
Why
Correct — A, A-4, B-1, C-2, D-3. Atomicity is the number of atoms in one molecule of an element. White phosphorus exists as P4 (atomicity 4, List II item 4), nitrogen as N2 (atomicity 2, item 1), neon is a monatomic noble gas (atomicity 1, item 2), and sulphur exists as S8 rings (atomicity 8, item 3). Matching each element to its atomicity gives A-4, B-1, C-2, D-3.
Why the others are wrong
- (b)A-4, B-2, C-1, D-3 — It swaps nitrogen and neon, making nitrogen monatomic and neon diatomic. In reality nitrogen is diatomic (N2) and neon is monatomic, so the pairing is wrong.
- (c)A-3, B-2, C-1, D-4 — It gives phosphorus atomicity 8 and sulphur atomicity 4, reversing the two, and also mishandles nitrogen and neon. Phosphorus is P4 (4) and sulphur is S8 (8).
- (d)A-3, B-1, C-2, D-4 — Nitrogen and neon are matched correctly, but it assigns phosphorus atomicity 8 and sulphur atomicity 4 — the wrong way round, since P4 has 4 atoms and S8 has 8.
Concept
Atomicity is the number of atoms present in one molecule of an element. Noble gases such as helium and neon are monatomic (atomicity 1); most common gaseous elements like hydrogen, nitrogen and oxygen are diatomic (atomicity 2); while some non-metals form larger molecules — phosphorus as P4 and sulphur as S8.
Each element needs only its molecular formula — P4, N2, Ne (a single atom) and S8. Reading off the subscript gives the atomicity directly. The only care needed is matching those values to List II, where the item numbers 1 to 4 are labels and are not the same as the atomicity values they stand for.
Key facts
- Atomicity is the number of atoms in one molecule of an element.
- Noble gases such as helium, neon and argon are monatomic; hydrogen, nitrogen, oxygen and the halogens are diatomic.
- White phosphorus exists as P4 (atomicity 4) and sulphur commonly exists as S8 rings (atomicity 8).
- Ozone (O3) is triatomic — a reminder that atomicity depends on the molecule, not just the element.
Reading each molecular formula gives the atomicity — Ne 1, N2 2, P4 4, S8 8 — so A-4, B-1, C-2, D-3, which is option (a).
Study next
Common traps
- Atomicity means atoms per molecule of an element — it is not the valency or the atomic number.
- In a match-the-list item the List II serial numbers are only labels; do not confuse the label '1' with the atomicity value it points to.
Atomicity is asked as 'which element is monatomic, diatomic or polyatomic' or as a match-the-columns item — recall the molecular formula and read off the number of atoms.
Related PYQs
Which one among the following elements is polyatomic?
- (a) Phosphorus
- (b) Sulphur
- (c) Chlorine
- (d) Aluminium
Answer(b) Sulphur
The same concept of atomicity. There the task is to spot the polyatomic element (sulphur, S8) against diatomic chlorine and tetra-atomic phosphorus; here the same atomicities (P4, N2, Ne, S8) have to be matched to their values.
Practice
- practice — not a real PYQ
Which one of the following elements is monatomic?
- (a)Nitrogen
- (b)Oxygen
- (c)Helium
- (d)Chlorine
Answer(c) Helium — noble gases exist as single atoms, so their atomicity is 1. - practice — not a real PYQ
The atomicity of sulphur in its common solid form is
- (a)1
- (b)2
- (c)4
- (d)8
Answer(d) 8 — sulphur exists as S8 ring molecules.