Explanation

• An electron carries a negative electric charge.
• Its charge is approximately −1.602 × 10⁻¹⁹ C.
• A proton has an equal magnitude of positive charge, while a neutron has zero electric charge.
• The charge of an electron is called the elementary charge with a negative sign.

Explanation

Oxidation is the chemical process of:

• Losing electrons
• Oxidation state increases
• Always paired with reduction (together form redox)
• Reducing agent gets oxidized (it gives up the electrons)

Additional information 

Reduction:

• Gain electrons
• Oxidation state lowers
• Always paired with oxidation (redox)
• Oxidizing agent gets reduced

Last verified on 22-10-2026

Explanation

• Arsenic is a toxic substance that can contaminate groundwater and cause serious health problems after prolonged exposure.
• Water sources confirmed to have excessive arsenic should be clearly marked, and people should be advised not to use them for drinking or cooking.

Last verified on 21-10-2026

Explanation

• Nitrogen (N₂) makes up about 78% of Earth's atmosphere. 
• It is generally not considered an air pollutant in its normal form.

Additional information:

• Hydrocarbons can contribute to air pollution by reacting with nitrogen oxides to form ground-level ozone.
• Chromium, especially certain compounds such as hexavalent chromium, can pollute the air and pose serious health risks.
• Carbon dioxide (CO₂) is a greenhouse gas that contributes to global warming and is also classified as an air pollutant in some environmental frameworks.

Last verified on 21-10-2026

Explanation

• Sulphur dioxide (SO₂) is used as a dechlorinating agent to remove residual chlorine from water.
• It reacts with chlorine and reduces it to chloride ions, thereby neutralizing its disinfecting effect.
• Dechlorination is commonly required when excess chlorine must be removed from treated water or wastewater.

Last verified on 17-10-2026