Classification of elements and Periodicity in properties MCQs for NEET — Chemistry Questions with Answers

(a) Correct order of electron affinity is : Cl>F>S>O

     Electron affinity of 2nd period non-metals is less than that of respective 3rd period non-metals.

(d) According to Allred and Rochow scale

Electronegativity =$0.359\frac{Z_{eff.}}{r^2}+0.744$

(a) Nitrogen has stable $2p^3$ configuration and also due to high $e^{-}$ charge density at outermost orbital it requires energy to add one extra $e^{-}$ in its outer most shell i.e., its first electron gain enthalpy is positive.

(a) LiF is sparingly soluble at room temperature due to its high lattice energy.

(a) Oxidation state of non- metal increases acidic nature of oxide increase $\stackrel{+7}{C{l}_2{O}_7}$ is most acidic.

(b) Sum of oxidation numbers of all atoms in a neutral molecule is zero.

 $$\begin{gathered} \to A_3{\left(B_{4}C\right)}_2 : +2\times 3+2\times \left[4\times 5-2\right]=42\ne 0 \\ \to A_3{\left(B{C}_4\right)}_2 : +2\times 3+2\times \left[+5-8\right]=0 \\ \to A_2{\left(B{C}_3\right)}_2 : +2\times 2+2\times \left[+5-6\right]=+2\ne 0 \\ \to AB{C}_2 : +2+5+\left(-2\right)\times 2=+3\ne 0 \end{gathered}$$

(c) Possible elements  Period number   Group number   Electronic configuration

  (i)          H                       1                      1                           $1s^1$

  (ii)         Be                      2                      2                           $1s^{1}2s^2$

(b) Atomic radius and nuclear charge increases from top to bottom because number of shell and atomic mass increases down the group.

(a) $L{a}^{3+}>G{d}^{3+}>E{u}^{3+}>L{u}^{3+}$ is incorrect due to lanthanide contraction because size will decrease from La+3 to Lu+3.

(d) Second ionization energy is amount of energy required to take out an electron from the monopositive cation.

Hence, $$\begin{gathered} M_{\left(g\right)}\to M^{2+}2e^{-} \\ {M}_{\left(g\right)}\to M^{+}+e^{-} \end{gathered}$$