JEE Main 2026 — Apr 2, Shift 2 — Chemistry solution

JEE Main2026Apr 2, Shift 2Chemistry

Number of paramagnetic ions among the following d- and f-block metal ions is _________.

Mn $^{2 +}$ , Cu $^{2 +}$ , Zn $^{2 +}$ , Yb $^{2 +}$ , Sc $^{3 +}$ , La $^{3 +}$ , Gd $^{3 +}$ , Lu $^{3 +}$ , Ti $^{4 +}$ , Ce $^{4 +}$

(Atomic number of Mn $= 25$ , Cu $= 29$ , Zn $= 30$ , Yb $= 70$ , Sc $= 21$ , La $= 57$ , Gd $= 64$ , Lu $= 71$ , Ti $= 22$ , Ce $= 58$ )

Your answer

Solution

Examine the $d$ / $f$ electron count of each ion:

Mn $^{2 +}$ : $[Ar] 3 d^{5}$ — $5$ unpaired electrons, paramagnetic. $✓$

Cu $^{2 +}$ : $[Ar] 3 d^{9}$ — $1$ unpaired, paramagnetic. $✓$

Zn $^{2 +}$ : $3 d^{10}$ — diamagnetic.

Yb $^{2 +}$ : $[Xe] 4 f^{14}$ — diamagnetic.

Sc $^{3 +}$ , La $^{3 +}$ , Lu $^{3 +}$ , Ti $^{4 +}$ , Ce $^{4 +}$ : all have empty $d$ / $f$ shells ( $d^{0}$ or $f^{0}$ / $f^{14}$ ) — diamagnetic.

Gd $^{3 +}$ : $[Xe] 4 f^{7}$ — $7$ unpaired, paramagnetic. $✓$

Total paramagnetic ions: $3$ (Mn $^{2 +}$ , Cu $^{2 +}$ , Gd $^{3 +}$ ).

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