MCQ
$B$ has a smaller first ionization enthalpy than $Be$. Consider the following statements :

$(I)$ It is easier to remove $2 \mathrm{p}$ electron than $2 \mathrm{s}$ electron

$(II)$ $2 \mathrm{p}$ electron of $\mathrm{B}$ is more shielded from the nucleus by the inner core of electrons than the $2 s$ electrons of $Be.$

$(III)\; 2 s$ electron has more penetration power than $2 \mathrm{p}$ electron.

$(IV)$ atomic radius of $\mathrm{B}$ is more than $\mathrm{Be}$

(Atomic number $\mathrm{B}=5, \mathrm{Be}=4$ )

The correct statements are

  • $(I), (II)$ and $(III)$
  • B
    $(II), (III)$ and $(IV)$
  • C
    $(I), (III)$ and $(IV)$
  • D
    $(I), (II)$ and $(IV)$

Answer

Correct option: A.
$(I), (II)$ and $(III)$
a
$\mathrm{Be} \Rightarrow 1 \mathrm{s}^{2} 2 \mathrm{s}^{2}$

$\mathrm{B} \Rightarrow 1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{p}^{1}$

$\mathrm{B}$ has a smaller size than $Be$

it is easier to remove $2 \mathrm{p}$ electron than $2 \mathrm{s}$

electron due to less pentration effect of $2 \mathrm{p}$ than $2 \mathrm{s}$

$2 \mathrm{p}$ electron of Boron is more shielded from the nucleus by the inner core of electron than the $2 \mathrm{s}$ electron of $\mathrm{Be}$

$B$ has a smaller size than $Be$

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