The number of maximum electrons in N Shell is
- (a)2
- (b)8
- (c)18
- (d)32
Correct — D, 32. The maximum number of electrons a shell can hold is 2n2, where n is the shell number. The N shell is the fourth shell (K=1, L=2, M=3, N=4), so its capacity is 2 x 4 squared = 2 x 16 = 32 electrons.
- (a)2 — 2 is the capacity of the first (K) shell, where n = 1 gives 2 x 1 squared = 2.
- (b)8 — 8 is the capacity of the second (L) shell, where n = 2 gives 2 x 2 squared = 8.
- (c)18 — 18 is the capacity of the third (M) shell, where n = 3 gives 2 x 3 squared = 18.
Electron shells are labelled K, L, M, N for the principal quantum numbers n = 1, 2, 3, 4. Each shell holds at most 2n2 electrons, so the capacities run 2, 8, 18 and 32. The outermost shell of a stable neutral atom, however, never holds more than 8 (the octet rule).
Recognise 'N shell' as the fourth shell, then apply 2n2 with n = 4. The three distractors are simply the capacities of the earlier shells.
- The maximum number of electrons in a shell equals 2n2.
- K, L, M and N shells correspond to n = 1, 2, 3, 4.
- Their capacities are 2, 8, 18 and 32 electrons respectively.
- The outermost shell holds at most 8 electrons in a stable neutral atom (octet rule).
- Reading 'N shell' as the first shell instead of the fourth.
- Forgetting to square n in the 2n2 formula.
Asked by naming a shell (K/L/M/N) and asking its maximum electron capacity via 2n2.
No directly related past PYQ was found.
- practice — not a real PYQ
The maximum number of electrons that the M shell can hold is
- (a)2
- (b)8
- (c)18
- (d)32
Answer(c) 18 — from 2 x 3 squared for n = 3.
- practice — not a real PYQ
The rule giving the maximum number of electrons in a shell is
- (a)n squared
- (b)2n
- (c)2n squared
- (d)n + 2
Answer(c) 2n squared, where n is the shell number.