Class 9 Chemistry – Chapter: Structure of Atom – 50 Important MCQs for Junior Science Teacher Test
MCQs
Q1. Who discovered the electron?
اŮŰڊٚعا٠ڊ٠ڊس ŮŰ ŘŻŘąŰاŮŘŞ ÚŠŰا؟
a) John Dalton
b) J.J. Thomson
c) Ernest Rutherford
d) James Chadwick
Explanation: J.J. Thomson discovered the electron in 1897 using cathode ray tube experiments.
Q2. The charge on an electron is:
اŮŰڊٚعا٠ٞع Úاع؏ ÚŠŰا ŰŮتا ŰŰ؟
a) Positive
b) Neutral
c) Negative
d) Double positive
Explanation: Electrons carry a negative electric charge.
Q3. Who discovered the nucleus of the atom?
اŰŮšŮ
ÚŠŰ ŮŰŮÚŠŮŘŚŰŘł ÚŠŮ ÚŠŘł ŮŰ ŘŻŘąŰاŮŘŞ ÚŠŰا؟
a) J.J. Thomson
b) John Dalton
c) Ernest Rutherford
d) Niels Bohr
Explanation: Rutherford discovered the nucleus through the gold foil experiment.
Q4. Proton carries which charge?
ٞعŮŮšŮ٠ٞع ÚŠŮ٠سا Úاع؏ ŰŮتا ŰŰ؟
a) Negative
b) Positive
c) Neutral
d) Double negative
Explanation: Protons are positively charged particles present in the nucleus.
Q5. Neutron was discovered by:
ŮŰŮٚعا٠ڊ٠ڊس ŮŰ ŘŻŘąŰاŮŘŞ ÚŠŰا؟
a) Rutherford
b) Thomson
c) James Chadwick
d) Dalton
Explanation: James Chadwick discovered the neutron in 1932.
Q6. The nucleus of an atom contains:
اŰŮšŮ
ÚŠŰ ŮŰŮÚŠŮŘŚŰŘł Ů
ŰÚş ÚŠŰا ŰŮتا ŰŰ؟
a) Electrons only
b) Protons and neutrons
c) Protons only
d) Neutrons only
Explanation: The nucleus consists of protons and neutrons.
Q7. Electrons revolve around the nucleus in:
اŮŰڊٚعا٠ŮŰŮÚŠŮŘŚŰŘł ÚŠŰ ÚŻŘąŘŻ ÚŠŰاں گعدش ÚŠŘąŘŞŰ ŰŰÚş؟
a) Energy levels or shells
b) Nucleus
c) Proton layers
d) Neutron cloud
Explanation: Electrons move in fixed energy levels called shells.
Q8. Atomic number represents:
اŰŮšŮ
Ű ŘšŘŻŘŻ ÚŠŰا ظاŰŘą ڊعتا ŰŰ؟
a) Number of neutrons
b) Number of protons
c) Number of shells
d) Atomic mass
Explanation: Atomic number equals the number of protons in the nucleus.
Q9. Mass number is the sum of:
ÚŠŮ
ŰŘŞŰ ŘšŘŻŘŻ ÚŠŘł ڊا Ů
ŘŹŮ
ŮŘšŰ ŰŮتا ŰŰ؟
a) Protons and neutrons
b) Protons and electrons
c) Electrons and neutrons
d) Shells and electrons
Explanation: Mass number equals the total number of protons and neutrons.
Q10. The smallest particle of an element is:
ÚŠŘłŰ ŘšŮؾع ڊا سب ŘłŰ ÚÚžŮٚا Ř°ŘąŰ ÚŠŰا ŰŮتا ŰŰ؟
a) Molecule
b) Ion
c) Compound
d) Atom
Explanation: Atom is the smallest particle that retains the chemical properties of an element.
Q11. An atom is electrically:
اŰŮšŮ
بعŮŰ ŘˇŮŘą ٞع ÚŠŰسا ŰŮتا ŰŰ؟
a) Positive
b) Negative
c) Neutral
d) Double charged
Explanation: In a neutral atom, the number of protons equals the number of electrons.
Q12. The relative mass of an electron is approximately:
اŮŰÚŠŮšŘąŘ§Ů ÚŠŰ ŮŘłŘ¨ŘŞŰ ÚŠŮ
ŰŘŞ ŘŞŮŘąŰباً ÚŠŰا ŰŰ؟
a) Equal to proton
b) 1/1836 of proton
c) Double of proton
d) Half of proton
Explanation: The mass of an electron is approximately 1/1836 the mass of a proton.
Q13. The center of an atom is called:
اŰŮšŮ
ÚŠŰ Ů
عڊز ÚŠŮ ÚŠŰا ÚŠŰŘŞŰ ŰŰÚş؟
a) Shell
b) Orbit
c) Nucleus
d) Electron cloud
Explanation: The nucleus is the dense central part of an atom.
Q14. Which particle has no charge?
ÚŠŮ٠سا Ř°ŘąŰ Ř¨ŘşŰŘą Úاع؏ ÚŠŰ ŰŮتا ŰŰ؟
a) Proton
b) Electron
c) Neutron
d) Positron
Explanation: Neutrons are neutral particles.
Q15. Maximum electrons in the first shell are:
ŮžŰŮŰ ŘŽŮŮ Ů
ŰÚş زŰŘ§ŘŻŰ ŘłŰ Ř˛ŰŘ§ŘŻŰ ÚŠŘŞŮŰ Ř§ŮŰڊٚعا٠ŰŮ ŘłÚŠŘŞŰ ŰŰÚş؟
a) 8
b) 18
c) 2
d) 32
Explanation: According to the 2n² rule, the first shell can hold a maximum of 2 electrons.
Q16. Maximum electrons in the second shell are:
ŘŻŮŘłŘąŰ ŘŽŮŮ Ů
ŰÚş زŰŘ§ŘŻŰ ŘłŰ Ř˛ŰŘ§ŘŻŰ ÚŠŘŞŮŰ Ř§ŮŰڊٚعا٠ŰŮ ŘłÚŠŘŞŰ ŰŰÚş؟
a) 2
b) 8
c) 18
d) 32
Explanation: The second shell can contain a maximum of 8 electrons.
Q17. Which scientist proposed the nuclear model of atom?
ÚŠŘł سا،Ůسدا٠ŮŰ Ř§ŰŮšŮ
ڊا ŮŰŮÚŠŮŰŘŚŘą Ů
اÚŮ ŮžŰŘ´ ÚŠŰا؟
a) Rutherford
b) Dalton
c) Thomson
d) Bohr
Explanation: Rutherford proposed the nuclear model after the gold foil experiment.
Q18. Thomson proposed which atomic model?
تڞاŮ
س٠ŮŰ ÚŠŮ٠سا اŰŮšŮ
Ű Ů
اÚŮ ŮžŰŘ´ ÚŠŰا؟
a) Nuclear model
b) Plum pudding model
c) Bohr model
d) Solid sphere model
Explanation: Thomson described the atom as a positively charged sphere with embedded electrons.
Q19. Bohr proposed that electrons move in:
بŮŰŘą ÚŠŰ Ů
ءاب٠اŮŰڊٚعا٠ڊŰاں ŘŘąÚŠŘŞ ÚŠŘąŘŞŰ ŰŰÚş؟
a) Random paths
b) Fixed energy levels
c) Inside nucleus
d) Neutron shells
Explanation: Bohr proposed that electrons revolve in fixed energy levels.
Q20. The K shell represents:
K ŘŽŮŮ ÚŠŘł ڊ٠ظاŰŘą ڊعتا ŰŰ؟
a) First energy level
b) Second energy level
c) Third energy level
d) Fourth energy level
Explanation: The K shell is the first and closest energy level to the nucleus.
Q21. Proton is represented by:
ٞعŮŮšŮŮ ÚŠŰ ŘšŮاŮ
ŘŞ ÚŠŰا ŰŰ؟
a) e⁻
b) p⁺
c) n⁰
d) e⁺
Explanation: Proton is represented by the symbol p⁺.
Q22. Neutron is represented by:
ŮŰŮŮšŘąŘ§Ů ÚŠŰ ŘšŮاŮ
ŘŞ ÚŠŰا ŰŰ؟
a) p⁺
b) e⁻
c) n⁰
d) e⁺
Explanation: Neutron is represented by n⁰ because it carries no charge.
Q23. Atomic mass unit is abbreviated as:
اŰŮšŮ
Ű ÚŠŮ
ŰŘŞŰ Ř§ÚŠŘ§ŘŚŰ ÚŠŮ Ů
؎تؾع ÚŠŰŘłŰ ŮÚŠÚžŘŞŰ ŰŰÚş؟
a) kg
b) amu
c) gm
d) mol
Explanation: Atomic masses are commonly expressed in atomic mass units (amu).
Q24. An atom becomes an ion when:
اŰŮšŮ
آ،٠ڊب بŮتا ŰŰ؟
a) It gains neutrons
b) It loses or gains electrons
c) It gains protons
d) It loses neutrons
Explanation: An ion forms when an atom gains or loses electrons.
Q25. Positive ion is called:
Ů
؍بت آ،٠ڊ٠ڊŰا ÚŠŰŘŞŰ ŰŰÚş؟
a) Anion
b) Cation
c) Molecule
d) Atom
Explanation: A positively charged ion is called a cation.
Q26. Negative ion is called:
Ů
ŮŮŰ Ř˘ŘŚŮ ÚŠŮ ÚŠŰا ÚŠŰŘŞŰ ŰŰÚş؟
a) Atom
b) Cation
c) Anion
d) Molecule
Explanation: A negatively charged ion is called an anion.
Q27. Particles present in nucleus are called:
ŮŰŮÚŠŮŘŚŰŘł Ů
ŰÚş Ů
ŮŘŹŮŘŻ ذعات ÚŠŮ ÚŠŰا ÚŠŰŘŞŰ ŰŰÚş؟
a) Nucleons
b) Electrons
c) Ions
d) Molecules
Explanation: Protons and neutrons together are called nucleons.
Q28. Hydrogen atomic number is:
Űا،ŰÚŘąŮ؏٠ڊا اŰŮšŮ
Ű ŘšŘŻŘŻ ÚŠŰا ŰŰ؟
a) 2
b) 3
c) 1
d) 4
Explanation: Hydrogen contains one proton, so its atomic number is 1.
Q29. Helium atomic number is:
ŰŰŮŰŮ
ڊا اŰŮšŮ
Ű ŘšŘŻŘŻ ÚŠŰا ŰŰ؟
a) 4
b) 2
c) 1
d) 8
Explanation: Helium contains two protons in its nucleus.
Q30. Carbon atomic number is:
ڊاعب٠ڊا اŰŮšŮ
Ű ŘšŘŻŘŻ ÚŠŰا ŰŰ؟
a) 6
b) 8
c) 12
d) 14
Explanation: Carbon has six protons in its nucleus.
Q31. The number of electrons in neutral carbon atom is:
ŘşŰŘą باع داع ڊاعب٠اŰŮšŮ
Ů
ŰÚş ÚŠŘŞŮŰ Ř§ŮŰڊٚعا٠ŰŮŘŞŰ ŰŰÚş؟
a) 12
b) 8
c) 6
d) 4
Explanation: Neutral atoms have equal numbers of protons and electrons.
Q32. Isotopes are atoms of the same element having:
آ،سŮŮšŮٞس اŰÚŠ ŰŰ ŘšŮؾع ÚŠŰ ŮŰ Ř§ŰŮšŮ
ŰŮŘŞŰ ŰŰÚş ŘŹŮ Ů
ŰÚş:
a) Same atomic number
b) Different atomic number
c) Same electrons only
d) Same mass number
Explanation: Isotopes have the same number of protons but different numbers of neutrons.
Q33. Hydrogen isotopes include:
Űا،ŰÚŘąŮŘŹŮ ÚŠŰ Ř˘ŘŚŘłŮŮšŮٞس ÚŠŮŮ ŘłŰ ŰŰÚş؟
a) Oxygen and Nitrogen
b) Sodium and Chlorine
c) Protium, Deuterium, Tritium
d) Carbon and Oxygen
Explanation: Hydrogen has three isotopes: Protium, Deuterium and Tritium.
Q34. Isotopes differ in the number of:
آ،سŮŮšŮٞس ÚŠŘł تؚداد Ů
ŰÚş Ů
ŘŽŘŞŮŮ ŰŮŘŞŰ ŰŰÚş؟
a) Protons
b) Neutrons
c) Electrons
d) Shells
Explanation: Isotopes differ only in neutron number.
Q35. The size of nucleus is:
ŮŰŮÚŠŮŘŚŰŘł ڊا ŘŘŹŮ
ÚŠŰسا ŰŮتا ŰŰ؟
a) Very small
b) Very large
c) Equal to atom
d) Larger than atom
Explanation: The nucleus occupies a very small space compared to the atom.
Q36. Most of the mass of atom lies in:
اŰŮšŮ
ÚŠŰ Ř˛ŰŘ§ŘŻŰ ŘŞŘą ÚŠŮ
ŰŘŞ ÚŠŰاں ŰŮŘŞŰ ŰŰ؟
a) Electron cloud
b) Shells
c) Nucleus
d) Energy levels
Explanation: Protons and neutrons present in the nucleus contain most of the atomic mass.
Q37. Electrons remain in orbit due to:
اŮŰڊٚعا٠Ů
داع Ů
ŰÚş ÚŠŰŮÚş ŘąŰŘŞŰ ŰŰÚş؟
a) Electrostatic attraction
b) Friction
c) Magnetic force
d) Gravity
Explanation: Opposite charges between electrons and nucleus create electrostatic attraction.
Q38. Energy levels are named as:
ŘŞŮاŮŘ§ŘŚŰ ÚŠŰ ŘłŘˇŘŮÚş ÚŠŮ ÚŠŘł ŘˇŘąŘ ŮاŮ
ŘŻŰا ؏اتا ŰŰ؟
a) A, B, C
b) K, L, M, N
c) X, Y, Z
d) P, Q, R
Explanation: Electron shells are represented by letters K, L, M and N.
Q39. Atom becomes stable when:
اŰŮšŮ
ڊب Ů
ستŘÚŠŮ
ŰŮتا ŰŰ؟
a) Outer shell is complete
b) Inner shell empty
c) No electrons present
d) No neutrons present
Explanation: Atoms are stable when their outermost shell is complete.
Q40. The modern atomic theory describes electrons as:
ŘŹŘŻŰŘŻ اŰŮšŮ
Ű ŮظعŰŰ ÚŠŰ Ů
ءاب٠اŮŰڊٚعا٠ڊ٠ڊŰŘłŰ Ř¨Űا٠ڊŰا ؏اتا ŰŰ؟
a) Fixed particles
b) Solid balls
c) Electron cloud
d) Heavy particles
Explanation: Modern theory describes electrons as probability clouds around the nucleus.
Q41. Proton mass is approximately:
ٞعŮŮšŮŮ ÚŠŰ ÚŠŮ
ŰŘŞ ŘŞŮŘąŰباً ÚŠŘŞŮŰ ŰŮŘŞŰ ŰŰ؟
a) 1 amu
b) 0 amu
c) 5 amu
d) 10 amu
Explanation: The mass of a proton is approximately 1 atomic mass unit.
Q42. Electron symbol is:
اŮŰÚŠŮšŘąŘ§Ů ÚŠŰ ŘšŮاŮ
ŘŞ ÚŠŰا ŰŰ؟
a) p⁺
b) e⁻
c) n⁰
d) e⁺
Explanation: Electron is represented by the symbol e⁻.
Q43. Proton is located in:
ٞعŮŮšŮŮ ÚŠŰاں ٞاŰا ؏اتا ŰŰ؟
a) Electron cloud
b) Shell
c) Nucleus
d) Orbit
Explanation: Protons are present inside the nucleus of an atom.
Q44. Neutron is located in:
ŮŰŮٚعا٠ڊŰاں ٞاŰا ؏اتا ŰŰ؟
a) Nucleus
b) Shell
c) Orbit
d) Electron cloud
Explanation: Neutrons are present inside the nucleus.
Q45. Hydrogen atom contains:
Űا،ŰÚŘąŮŘŹŮ ÚŠŰ Ř§ŰŮšŮ
Ů
ŰÚş ÚŠŰا ŰŮتا ŰŰ؟
a) 1 proton and 1 electron
b) 2 protons
c) 2 electrons
d) 3 neutrons
Explanation: Hydrogen contains one proton and one electron.
Q46. Carbon-12 contains how many neutrons?
ڊاعبŮ-12 Ů
ŰÚş ÚŠŘŞŮŰ ŮŰŮٚعا٠ŰŮŘŞŰ ŰŰÚş؟
a) 6
b) 12
c) 8
d) 4
Explanation: Carbon-12 has 6 protons and 6 neutrons.
Q47. Atomic structure mainly studies:
اŰŮšŮ
Ű ŘłŘ§ŘŽŘŞ Ů
ŰÚş بŮŰŘ§ŘŻŰ ŘˇŮŘą ٞع ÚŠŰا ŮžÚڞا ؏اتا ŰŰ؟
a) Chemical reactions
b) Subatomic particles
c) Compounds
d) Mixtures
Explanation: Atomic structure deals with electrons, protons and neutrons.
Q48. The first atomic theory was proposed by:
ŮžŰŮا اŰŮšŮ
Ű ŮظعŰŰ ÚŠŘł ŮŰ ŮžŰŘ´ ÚŠŰا؟
a) Dalton
b) Rutherford
c) Bohr
d) Thomson
Explanation: John Dalton proposed the first modern atomic theory.
Q49. Rutherford model is also known as:
عدعŮŮŘąÚ Ů
اÚ٠ڊ٠اŮŘą ÚŠŘł ŮاŮ
ŘłŰ ŘŹŘ§Ůا ؏اتا ŰŰ؟
a) Plum pudding model
b) Nuclear model
c) Solid sphere model
d) Quantum model
Explanation: Rutherford model is known as the nuclear model of the atom.
Q50. The rule used to calculate maximum electrons in a shell is:
ÚŠŘłŰ ŘŽŮŮ Ů
ŰÚş زŰŘ§ŘŻŰ ŘłŰ Ř˛ŰŘ§ŘŻŰ Ř§ŮŰڊٚعا٠Ů
ŘšŮŮŮ
ÚŠŘąŮŰ ÚŠŘ§ اؾŮŮ ÚŠŰا ŰŰ؟
a) 2n² rule
b) Newton rule
c) Dalton rule
d) Avogadro rule
Explanation: The maximum number of electrons in a shell is calculated using the 2n² rule.
Answer Key
1.b
2.c
3.c
4.b
5.c
6.b
7.a
8.b
9.a
10.d
11.c
12.b
13.c
14.c
15.c
16.b
17.a
18.b
19.b
20.a
21.b
22.c
23.b
24.b
25.b
26.c
27.a
28.c
29.b
30.a
31.c
32.a
33.c
34.b
35.a
36.c
37.a
38.b
39.a
40.c
41.a
42.b
43.c
44.a
45.a
46.a
47.b
48.a
49.b
50.a
50/42 correct
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