NEET Practice Questions (MCQs) with Answers & Solutions

wavelength is inversely proportional to mass.

$$\begin{gathered} \because \frac{1}{\mathrm{\lambda }}=\mathrm{R}\left(\frac{1}{{\mathrm{n}}_1^2}-\frac{1}{{\mathrm{n}}_2^2}\right); {\mathrm{n}}_1=1, {\mathrm{n}}_2=?; \\ \frac{1}{\mathrm{\lambda }}=\mathrm{R}\left(\frac{1}{1}-\frac{1}{{\mathrm{n}}_2^2}\right) \Rightarrow {\mathrm{n}}_2^2=\frac{\mathrm{R\lambda }}{\mathrm{R\lambda }-1} \\ \Rightarrow {\mathrm{n}}_2=\sqrt{\frac{\mathrm{\lambda R}}{\mathrm{\lambda R}-1}} \end{gathered}$$

$$\begin{gathered} \mathrm{E}={\mathrm{E}}_1+{\mathrm{E}}_2; \frac{\mathrm{hc}}{\mathrm{\lambda }}=\frac{\mathrm{hc}}{{\mathrm{\lambda }}_1}+\frac{\mathrm{hc}}{{\mathrm{\lambda }}_2} \\ \Rightarrow \frac{\mathrm{hc}}{\mathrm{\lambda }}\mathrm{hc} \left(\frac{{\mathrm{\lambda }}_2+{\mathrm{\lambda }}_1}{{\mathrm{\lambda }}_1{\mathrm{\lambda }}_2}\right); \mathrm{\lambda }=2\frac{{\mathrm{\lambda }}_1{\mathrm{\lambda }}_2}{{\mathrm{\lambda }}_1+{\mathrm{\lambda }}_2} \end{gathered}$$

10 th element is neon, which is last element of 2nd period.

SInce size increases down the period , thus bond dissociation energy decreases, F2 is exception to this trend.

(c)  Al₂O₃ are amphoteric oxides

Newland's Octaves Law -

Arranged the element in increasing order of their atomic weight and found that every eighth element had properties similar to that of the first element. Law of Octave was found to be true upto calcium.

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An element having configuration ns2 np1 will show +3 OS and its oxide nature will be that of its group i.e. Baron, Aluminium, etc.

therefore X2O3, and amphoteric nature. B2O3 is acidic , but tht is not in option , so only 3 is right ans.

(c) It belongs to general outer electronic configuration of halogens which are most electronegative elements.

(c) The metallic character is maximum in I gp. elements.

  EN increase along the period

(b) Non-metallic character increases along the period and decreases down the gp.