Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in $C_2H_4$ and $C_2H_2$ molecules.

The total number of sigma $(\sigma)$ and pi $(\pi)$ bonds in an ethylene molecule are

Among the following ions,the $p\pi - d\pi$ overlap could be present in:

Match the orbital overlap figures shown in List-$I$ with the description given in List-$II$ and select the correct answer using the code given below the lists.
List-$I$:
$P$. Two $d$-orbitals overlapping axially with same phase.
$Q$. $A$ $p$-orbital and a $d$-orbital overlapping laterally with same phase.
$R$. $A$ $p$-orbital and a $d$-orbital overlapping laterally with opposite phase.
$S$. Two $d$-orbitals overlapping axially with opposite phase.
List-$II$:
$1$. $p-d$ $\pi$ antibonding
$2$. $d-d$ $\sigma$ bonding
$3$. $p-d$ $\pi$ bonding
$4$. $d-d$ $\sigma$ antibonding
Codes: $P \quad Q \quad R \quad S$

Number of $\sigma$ and $\pi$ bonds present in $CH_3-CH=CH-C\equiv CH$ are

If the internuclear axis is the $z$-axis,then in which of the following cases are $\sigma$ and $\pi$ bonds not possible?