JEE Main · 2020 · Shift-IhardPERI-090

B has a smaller first ionization enthalpy than Be. The correct statements are: (I) It is easier to remove 2p electron…

Classification of Elements & Periodicity · Class 11 · JEE Main Previous Year Question

Question

B has a smaller first ionization enthalpy than Be. The correct statements are:

(I) It is easier to remove 2p electron than 2s electron. (II) 2p electron of B is more shielded from the nucleus by the inner core of electrons than the 2s electrons of Be. (III) 2s electron has more penetration power than 2p electron. (IV) Atomic radius of B is more than Be.

Options
  1. a

    (I), (II) and (IV)

  2. b

    (II), (III) and (IV)

  3. c

    (I), (II) and (III)

  4. d

    (I), (III) and (IV)

Correct Answerc

(I), (II) and (III)

Detailed Solution

🧠 B < Be in IE1IE_1 because B's 2p12p^1 electron is higher in energy AND better shielded — but B's atomic radius is SMALLER than Be (statement IV is the false one) Boron has one more proton than beryllium. In the same period, more protons means a tighter atom — so B is smaller than Be. The lower IE of B has nothing to do with size; it comes from orbital energy differences.

🗺️ Evaluate each statement (I) "It is easier to remove the 2p2p electron than the 2s2s electron": 2p2p is at higher energy than 2s2s in a multi-electron atom. So yes, 2p2p is easier. True.

(II) "B's 2p2p electron is more shielded than Be's 2s2s electron": B's 2p2p is shielded by both the 1s21s^2 core AND the 2s22s^2 subshell sitting beneath it. Be's 2s2s is shielded by only 1s21s^2. So B's outer electron experiences more shielding. True.

(III) "2s2s has more penetration power than 2p2p": 2s2s orbitals have a small inner lobe near the nucleus that 2p orbitals don't. So 2s2s penetrates more. True.

(IV) "B has bigger atomic radius than Be": B = 88 pm, Be = 111 pm. Wait — actually Be > B in radius. So the statement is FALSE.

Correct: I, II, III.

⚠️ The trap Statement (IV) is the killer. Students see "B has more electrons than Be" and think "more electrons = bigger atom". But in the same period, the dominant factor is increasing nuclear charge, which shrinks the atom. Be → B → C → ... → F all shrink left to right. So Be is bigger than B, not smaller.

Answer: (c)\boxed{\text{Answer: (c)}}

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B has a smaller first ionization enthalpy than Be. The correct statements are: (I) It is easier to… (JEE Main 2020) | Canvas Classes