NEET Chemistry Chapter 3 Atoms And Molecules Question And Answers

NEET Chemistry Chapter 3 Atoms And Molecules Question And Answers

Question 1. Name two elements which exists independently.
Answer.

Helium and neon are two elements which exists independently.

Question 2. Define an atom.
Answer.

Atom:

An atom is the smallest unit of matter which has the chemical properties of the element.

Question 3. What is atomic mass?
Answer.

Atomic Mass:

The amount of the total number of protons and neutrons present in the nucleus of an atom is called atomic mass.

Question 4. Define valency.
Answer.

Valency:

Valency is a tendency in an atom to achieve the state of stability by achieving 8 electrons in its outermost shell by receiving, leaving or sharing of electrons from other atoms.

Question 5. What are homonuclear molecules?
Answer.

Homonuclear molecules:

Homonuclear molecules are those molecules in which same type of atoms are present.

Example H₂, Cl₂ etc.

Question 6. What are heteronuclear molecules?
Answer.

Heteronuclear Molecules:

Heteronuclear molecules are those molecules in which different type of atoms are present.

Example, H₂O, CO₂ etc.

Question 7. What are polyatomic ions?
Answer.

Polyatomic ions:

A group of atoms that carry a charge is called polyatomic ion. Example NH4⁺, CO₃^2- etc.

Question 8. Why were the rehabilitation centres and health spas made in forest areas?
Answer.

The forests besides giving fresh and unpolluted air, also naturally provide negative ions which neutralises the harmful effects of positive ions.

Question 9. What does a chemical formula tell us about?
Answer.

Chemical formula:

A chemical formula tells us about the elements present in a compound along with their number.

Question 10. State the chemical formula of the compound formed between Hydrogen and Sulphur.
Answer.

Chemical formula of the compound formed between Hydrogen and Sulphur:

Valency of Hydrogen = 1

Valency of Sulphur = 2

Compound of Hydrogen and Sulphur = H₂S

Question 11. An element ‘A’ forms a compound A₂O₃. What according to you is the valency of A?
Answer.

An element ‘A’ forms a compound A₂O₃.

The valency of A will be 3.

Question 12. An element has a valency of 2. What will be the formula for its oxide?
Answer.

An element has a valency of 2.

Valency of the element (X) = 2

Valency of Oxygen = 2

Formula for its oxide = XO