In the herbicide linuron whose structure is shown in the image attached, there are four pi bonds.
A pi bond is formed by a sideways overlap of atomic orbitals. A sigma bond is formed by an end to end or head to head overlap of atomic orbitals. Pi bonds lead to the occurrence of multiple bonds in the molecule.
In the herbicide linuron whose structure is shown in the image attached to this answer, there are four pi bonds which are easily spotted as double bonds in the structure.
Antacid contains ingredients such as aluminum, calcium, magnesium and sodium bicarbonate which act as bases. These help neutralise the pH levels in the stomach and makes the contents of the stomach less corrosive.