Question

Statement 1 : The double bond in $C_2$ molecule consists of both $\pi$-bonds.
Statement 2 : Four electrons are present in two $\pi$-bonding molecular orbitals in $C_2$.

• A. If both Statement $1$ and Statement $2$ are true and the statement $2$ is the correct explanation of the statement $1$
• B. If both Statement $1$ and Statement $2$ are true but statement $2$ is not the correct explanation of the statement $1$
• C. If Statement $1$ is true but Statement $2$ is false
• D. If Statement $1$ is false but Statement $2$ is true

Answer 1

Answer: (A)

Both are true statements and the Statement $2$ in the correct explanation of Statement $1$.
$C_2:(\sigma 1s{)}^2({\sigma }^{\ast }1s{)}^2(\sigma 2s{)}^2({\sigma }^{\ast }2s{)}^2({\sigma }^{\ast }2p_x^2=\pi 2p_y^2)$ or $KK$
$(\sigma 2s{)}^2({\sigma }^{\ast }2s{)}^2(\pi 2p_x^2=\pi 2p_y^2)$
The bond order of $C_2$ is $1/2(8-4)=2$ and $C_2$ should be diamagnetic. It is important to note that double bond in $C_2$ consists of both pi bonds because of the presence of four electrons in two pi molecular orbitals. In most of the other molecules a double bond is made up of a sigma bond and a pi bond.