Question

How many orbitals are having higher energy compared to ${\sigma }_{2S}$ for $L{i}_2$ molecule from the molecular orbitals given below.
${\sigma }^{\ast }1s,{\sigma }^{\ast }2s,\sigma 1s,\pi 2p_y,{\pi }^{\ast }2p_x,{\pi }^{\ast }2p_z,\pi 2p_z$

Answer 1

As we know the molecular electronic configuration is $\sigma 1s{\sigma }^{\ast }1s\sigma 2s{\sigma }^{\ast }2s\sigma 2p_x\Pi 2p_y=\Pi 2p_z$ etc.

Given are according to level of energy is:

$\sigma 1s<{\sigma }^{\ast }1s<{\sigma }^{\ast }2s<\Pi 2p_y<\Pi 2p_z<{\Pi }^{\ast }2p_x<{\Pi }^{\ast }2p_z$

$\downarrow$ $\downarrow$ $\downarrow$ $\downarrow$ $\downarrow$

$1$ $2$ $3$ $4$ $5$

$5$ molecular orbitals have high energy than $\sigma 2s$ .