Explanation

• Atoms of the same element always have the same atomic number.
• Sometimes, they differ in mass due to neutrons.
• Such atoms have identical chemical behavior.
• They differ only in mass number, not in properties.
• These are called isotopes.

Additional information:

• Radioactive isotopes are used in medicine and industry.
• Carbon-14 is used for age determination (carbon dating).

Last verified on 04-05-2026

Explanation

• Atomic number is a fundamental property of an element.
• It defines the identity of an element in the periodic table.
• It is based on particles present in the nucleus.
• Specifically, it depends on the number of protons.
• Each element has a unique atomic number.

Last verified on 04-05-2026

Explanation

• Brass is an alloy mainly made of copper and zinc.
• In air, there are various gases including oxygen, carbon dioxide, moisture, and traces of hydrogen sulphide (H₂S).
• The gas responsible for discoloration of brass is hydrogen sulphide.
• Hydrogen sulphide reacts with copper present in brass to form copper sulphide.
• This copper sulphide forms a dark layer, causing brass to lose its shine and colour (tarnishing).

Last updated question by NS on 2 MAY 2026

Explanation

• Tetraethyl lead is primarily used as an antiknock agent
• Octane booster in gasoline and aviation fuel.
•  It prevents "knocking" (premature ignition of petrol vapors) in motors.
• Highly toxic and easily absorbed through the skin, lungs, and gastrointestinal tract

Last updated question by NS on 2 MAY 2026

Explanation

• Atoms of the same element with same protons but different neutrons are called isotopes.
• They have the same atomic number but different mass numbers.
• Isotopes show different physical properties but similar chemical behavior.
• Example: Hydrogen has Protium, Deuterium, and Tritium.

Last verified on 02-05-2026