[Ad Space - Top: 728x90 or Responsive]
1What are canal rays?
Answer & Reference:
Canal rays are positively charged radiations produced in a gas discharge tube. They consist of protons. (Page 38)
2If an atom contains one electron and one proton, will it carry any charge?
Answer & Reference:
No, it is electrically neutral because +1 (proton) and –1 (electron) cancel out. (Page 38)
3On the basis of Thomson’s model, explain how the atom is neutral.
Answer & Reference:
Electrons (negative) are embedded in a sphere of positive charge, and the magnitudes are equal. (Page 39)
4Which sub-atomic particle is present in the nucleus?
Answer & Reference:
Protons (and neutrons) are in the nucleus. (Page 40)
5Name the three sub-atomic particles of an atom.
Answer & Reference:
Electron, proton, and neutron. (Page 41)
6Helium atom has atomic mass 4 u and 2 protons. How many neutrons?
Answer & Reference:
Mass number = protons + neutrons → 4 = 2 + n → 2 neutrons. (Page 41)
7Write electron distribution in carbon and sodium.
Answer & Reference:
Carbon (Z=6): 2, 4
Sodium (Z=11): 2, 8, 1
(Table 4.1, Page 43)
8If K and L shells are full, total electrons?
Answer & Reference:
K = 2, L = 8 → 10 electrons (Neon). (Page 42)
9How to find valency of chlorine, sulphur, magnesium?
Answer & Reference:
Chlorine (2,8,7): 1
Sulphur (2,8,6): 2
Magnesium (2,8,2): 2
(Table 4.1, Page 43–44)
10Atom has 8 electrons and 8 protons. (i) Atomic number? (ii) Charge?
Answer & Reference:
(i) Atomic number = 8
(ii) Charge = 0 (neutral)
(Page 44)
11Mass number of oxygen and sulphur?
Answer & Reference:
Oxygen: 16 (8p + 8n)
Sulphur: 32 (16p + 16n)
(Table 4.1, Page 43)
12Tabulate sub-atomic particles in H, D, T.
Answer & Reference:
| Isotope | Protons | Electrons | Neutrons |
|---|
| H | 1 | 1 | 0 |
| D | 1 | 1 | 1 |
| T | 1 | 1 | 2 |
(Pages 44–45)
13Compare properties of electron, proton, neutron.
Answer & Reference:
| Particle | Charge | Mass (u) | Location |
|---|
| Electron | –1 | ~0 | Outside nucleus |
| Proton | +1 | 1 | Nucleus |
| Neutron | 0 | 1 | Nucleus |
(Page 46)
14Limitations of Rutherford’s model?
Answer & Reference:
Could not explain atomic stability — revolving electrons should lose energy and fall into the nucleus. (Page 40)
15Describe Bohr’s model of the atom.
Answer & Reference:
Electrons revolve in discrete orbits (K, L, M...) without radiating energy. Orbits have fixed energy. (Page 41)
[Ad Space - Bottom: 300x250 or Responsive]