Atoms and Molecules Olympiad (8 Science)
NSO challenging questions on atomic structure, molecular composition, and chemical formulas. Olympiad-level logical reasoning on matter and substances.
TL;DR: NSO challenging questions on atomic structure, molecular composition, and chemical formulas. Olympiad-level logical reasoning on matter and substances…
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NSO challenging questions on atomic structure, molecular composition, and chemical formulas. Olympiad-level logical reasoning on matter and substances.
Atoms and Molecules Olympiad MCQs with Answers & Explanations
Q1. An atom has 6 protons. Its atomic number is 6. How many electrons does it have in a neutral state?
- 3
- 6 ✓ (correct)
- 12
- Cannot determine
Q2. What is the correct formula for the compound formed between calcium and chlorine?
- CaCl
- Ca2Cl
- CaCl2 ✓ (correct)
- Ca2Cl2
Q3. If the atomic mass of Oxygen is 16 and that of Carbon is 12, what is the molecular mass of CO2?
- 24
- 28
- 32
- 44 ✓ (correct)
Q4. An element has atomic number 7. To which group does it belong?
- Group 15 ✓ (correct)
- Group 16
- Group 17
- Group 18
Q5. Which of these represents an ionic compound?
- H2
- CO2
- NaCl ✓ (correct)
- CH4
Q6. A compound contains 2 hydrogen atoms and 1 sulfur atom. What is its formula?
- HS
- H2S ✓ (correct)
- H2S2
- S2H2
Q7. What is the valency of Nitrogen when it forms NH3?
- 1
- 3 ✓ (correct)
- 4
- 5
Q8. An atom becomes a positive ion by losing electrons. How many electrons did it lose if it went from 18 electrons to 16?
- 1
- 2 ✓ (correct)
- 3
- 4
Frequently Asked Questions
What is the difference between atomic number and mass number?
Atomic number is the number of protons in an atom's nucleus, which defines the element. Mass number is the total of protons and neutrons. For example, Carbon-12 has atomic number 6 (6 protons) and mass number 12 (6 protons + 6 neutrons). Atomic number determines chemical properties, while mass number distinguishes between isotopes of the same element.
How do we predict the formula of a compound from valencies?
Find the valencies of both elements. Write them as subscripts of the opposite element, then simplify to lowest terms. For example, Magnesium (valency +2) and Chlorine (valency -1): cross the valencies to get MgCl2. Aluminum (valency +3) and Oxygen (valency -2) gives Al2O3 after simplifying.
More 8 Science MCQs
- Light Reflection and Refraction
- Electricity
- Acids Bases and Salts
- Life Processes
- Carbon and its Compounds
- Metals and Non-metals
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