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1. What happens to an atom when it loses one electron?
A. Becomes negatively charged
B. Becomes positively charged
C. Becomes neutral
D. Becomes unstable isotope
2. The element with configuration 2,8,7 belongs to which group?
A. Alkali metals
B. Noble gases
C. Halogens
D. Alkaline earth metals
3. The isotope used in treatment of cancer is
A. Iodine-131
B. Uranium-235
C. Cobalt-60
D. Hydrogen-3
4. If K and L shells are full, how many electrons are there?
A. 8
B. 10
C. 18
D. 20
5. The number of electrons in sulphur atom (atomic number 16) is
A. 8
B. 16
C. 32
D. 6
6. Which one of the following is true about isotopes of chlorine?
A. Different atomic number
B. Same mass number
C. Different neutrons
D. Same number of neutrons
7. The electronic configuration of neon is
A. 2,6
B. 2,8
C. 2,8,1
D. 2,7
8. The maximum number of electrons in N shell is
A. 18
B. 24
C. 32
D. 40
9. What is the relation between atomic number and number of electrons in a neutral atom?
A. Atomic number = neutrons
B. Atomic number = protons
C. Atomic number = electrons
D. Both B and C
11. The electron distribution of phosphorus (Z=15) is
A. 2,8,5
B. 2,7,6
C. 2,8,8
D. 2,8,3
12. Which of the following atoms has a stable electronic configuration?
A. Sodium
B. Neon
C. Aluminium
D. Oxygen
14. Which scientist discovered the nucleus?
A. Bohr
B. Rutherford
C. Thomson
D. Goldstein
15. What was the main observation in Rutherford’s experiment?
A. All α-particles bounced back
B. Most passed straight through foil
C. None passed through foil
D. All deflected at large angles
16. Which one of the following is correct for a neutral atom of fluorine?
A. 9 protons, 9 electrons
B. 9 protons, 10 electrons
C. 9 neutrons, 9 protons
D. 10 neutrons, 9 electrons
17. If the ratio of chlorine isotopes (³⁵Cl:³⁷Cl) is 3:1, what percentage of ³⁷Cl is present?
A. 25%
B. 30%
C. 35%
D. 50%
19. Which postulate of Bohr’s model explains atomic stability?
A. Electrons radiate energy in orbit
B. Electrons occupy discrete energy levels
C. Nucleus contains neutrons
D. Electron paths are random
20. The number of protons in ³⁷₁₇Cl is
A. 17
B. 20
C. 37
D. 18
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