The double bond between the two carbon atoms in ethylene $(CH_2=CH_2)$ consists of:

Explain the characteristics of $\pi$ bonds. Or,give the requirements for the formation of $\pi$ bonds and explain the active centers.

Given below are two statements :
Statement $(I)$ : The oxidation state of an element in a particular compound is the charge acquired by its atom on the basis of electron gain enthalpy consideration from other atoms in the molecule.
Statement $(II)$ : $p\pi-p\pi$ bond formation is more prevalent in second period elements over other periods.
In the light of the above statements,choose the most appropriate answer from the options given below :

The total number of $\sigma$ and $\pi$-bonds present in the following compound is:

State the number of $\sigma$ and $\pi$ bonds in the following molecules:
$(a)$ $C_2H_2$
$(b)$ $C_2H_4$

$\pi$ bond is formed by: