Identify all the species that do not exist {H}₂^{+}, {He}₂²+}, {Li}₂²-}, {Ne}₂, {Be}₂^{-}, {He}₂

Correct Answer is : Li22−,Ne2,He2{Li}₂²-}, {Ne}₂, {He}₂Li22−,Ne2,He2 only

{Li}₂²-}, {Ne}₂, {He}₂ only

{Be}₂^{-}, {He}₂, {Ne}₂ only

Correct Answer is : Li22−,Ne2,He2{Li}₂²-}, {Ne}₂, {He}₂Li22−,Ne2,He2 only

Test Index

TS EAMCET 19-July-2022 Shift 2 Solved Paper

Section: Chemistry

Question : 126 of 160

Marks: +1, -0

\mathrm{H}_2^{+}, \mathrm{He}_2^{2+}, \mathrm{Li}_2^{2-}, \mathrm{Ne}_2, \mathrm{Be}_2^{-}, \mathrm{He}_2

Solution:

If the bond order of species is zero, then species will not exist.

Bond order

= \frac{\text{bonding molecular orbital electrons} - \text{ antibonding molecular orbital electrons }}{2}

\mathrm{H}_2^{+} - \sigma l s^1 \;\; \therefore

Bond order

= \frac{1-0}{2}=0.5

\mathrm{He}_2^{2+} - \sigma s^2 \;\; \therefore

Bond order

= \frac{2-0}{2}=1

\mathrm{Li}_2^{2-} - \sigma 1 s^2, \sigma^* 1 s^2, \sigma 2 s^2, \sigma^* 2 s^2

\therefore

Bond order

= \frac{4-4}{2}=0

(do not exist

)

\; \mathrm{Ne}_2: \sigma l s^2, \sigma^* 1 s^2, \sigma 2 s^2, \sigma^* 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2

\;\; \approx 2 p_y^2, \pi^* 2 p_x^2 \approx \pi^* 2 p_y^2, \sigma^* 2 p_z^2

\therefore

Bond order

= \frac{10-10}{2}=0

(do not exist)

\mathrm{Be}_2^{-} - \sigma 1 s^2, \sigma^* 1 s^2, \sigma 2 s^2, \sigma^* 2 s^2, \pi 2 p_x^1 \approx \pi 2 p_y^0

\therefore

Bond order

= \frac{5-4}{2}=0.5

\mathrm{He}_2 - \sigma l s^2, \sigma^* l s^2

\therefore

Bond order

= \frac{2-2}{2}=0(

do not exist

)

Hence,

\mathrm{Li}_2^{2-}, \mathrm{Ne}_2

and

\mathrm{He}_2

will not exist.

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