Question:

Which one of the following species does not exist under normal conditions?

Updated On: Apr 8, 2024
  • $Be_2^+$
  • $Be_2$
  • $B_2$
  • $Li_2$
Hide Solution
collegedunia
Verified By Collegedunia

The Correct Option is B

Solution and Explanation

Molecules with zero bond order, do not exist. According to molecular orbital theory,
(a) $Be_2^ + (4+4-1=7)$
$ \, \, \, \, \, \, \, \, \, \, \, \, \, = \sigma 1s^2, _{\sigma}^{*} 1s^2, \sigma 2s^2,_{\sigma}^{*} 2s^1 $
Bond order (BO) = $ \frac{4-3}{2}=0.5$
(b) $Be_2(4+5=8) = \sigma 1s^2 , _{\sigma}^{*} 1s^2, _{\sigma}^{*} 1s^2, \sigma 2s^2, _{\sigma}^{*} 2s^2$
$ \, \, \, \, \, \, \, \, BO = \frac{ 4-4}{2}= 0 $
(c) $B_2 (5+5=10)$
$ \, \, \, \, \, = \sigma 1s^2 , _{\sigma}^{*} 1s^2, \sigma 2s^2 ,_{\sigma}^{*} 2s^2,\pi 2 P_X^1 \approx \pi 2 P_Y^1$
Bond order (BO)= $\frac{6-4}{2} =1$
(d)$ Li_2(3+3=6) = \sigma1s^2,_{\sigma}^{*} 1s^2,\sigma2s^2$
$ \, \, \, \, \, \, \, BO = \frac{4-2}{2} =1$
Thus, $Be_2 $ does not exist under normal conditions.
Was this answer helpful?
1
0

Concepts Used:

Chemical Bonding and Molecular Structure

Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.

Types of Chemical Bonds:

There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds. 

  • Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
  • Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding. 
  • Hydrogen Bonds -  It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
  • Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.

Factors Affecting Bond Enthalpy in Chemical Bonding:

  • Size of the Atom
  • Multiplicity of Bonds
  • Number of Lone Pair of Electrons Present
  • Bond Angle