Chapter Exam

Chapter 9: Atomic Foundations of Matter — Online MCQ Test

Q: Which of the following is an element?

Answer: C. Iron — Iron is a pure substance made of only one kind of atom, so it is an element. Water, salt, and carbon dioxide are compounds.

Q: The symbol for sodium is:

Answer: B. Na — The chemical symbol for sodium is Na, derived from its Latin name, natrium.

Q: Which formula represents magnesium chloride?

Answer: B. MgCl2 — Magnesium has valency 2 and chlorine has valency 1, so the correct formula is MgCl2.

Q: Which of the following is NOT a correct statement about a molecule?

Answer: C. It always contains only one atom — A molecule can have one atom only in the case of noble gases, but it does not always contain only one atom. Many molecules have two or more atoms.

Q: Which of the following is the most appropriate formula mass of calcium hydroxide, Ca(OH)2?

Answer: C. 58 u — Formula mass of Ca(OH)2 = 40 + 2×(16 + 1) = 40 + 34 = 74 u.

SCIENCE · Grade 9 · CBSE(NCERT)

Practice Chapter 9: Atomic Foundations of Matter with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 9 SCIENCE. This chapter covers: Element Compound Molecule Valency Chemical Formula Atomic Mass Molecular Mass Law of Conservation of Mass Chemical Combination Symbol Equation Understanding atomic composition chem.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 9: Atomic Foundations of Matter — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 9 SCIENCE — Chapter 9: Atomic Foundations of Matter, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is an element?

A. Water
B. Salt
C. Iron ✓
D. Carbon dioxide

Answer: C. Iron
Iron is a pure substance made of only one kind of atom, so it is an element. Water, salt, and carbon dioxide are compounds.

The symbol for sodium is:

A. So
B. Na ✓
C. Sn
D. Sd

Answer: B. Na
The chemical symbol for sodium is Na, derived from its Latin name, natrium.

Which formula represents magnesium chloride?

A. MgCl
B. MgCl2 ✓
C. Mg2Cl
D. Mg2Cl2

Answer: B. MgCl2
Magnesium has valency 2 and chlorine has valency 1, so the correct formula is MgCl2.

Which of the following is NOT a correct statement about a molecule?

A. It is the smallest particle of a substance that can exist independently
B. It may contain atoms of the same element
C. It always contains only one atom ✓
D. It may contain atoms of different elements

Answer: C. It always contains only one atom
A molecule can have one atom only in the case of noble gases, but it does not always contain only one atom. Many molecules have two or more atoms.

Which of the following is the most appropriate formula mass of calcium hydroxide, Ca(OH)2?