If the mass number of an atom is A = 40 and its electron configuration is 1s22s22p63s23p6, the number of neutrons and protons in its nucleus will be 

(1) 22, 18           

(2) 18, 22

(3) 20, 20           

(4) 18, 18

Subtopic:  Mass-Energy Equivalent |
 76%
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Which of the following is most unstable

(1) Electrons           

(2) Protons

(3) Neutrons           

(4) α-particle

Subtopic:  Radioactivity (OLD NCERT) |
 56%
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 Radioactive substance do not emit

(1) Electron           

(2) Helium nucleus

(3) Positron         

(4) Proton

Subtopic:  Radioactivity (OLD NCERT) |
 57%
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During a negative beta decay 

1. An atomic electron is ejected
2. An electron which is already present within the nucleus is ejected
3. A neutron in the nucleus decays emitting an electron
4. A part of the binding energy is converted into electron
Subtopic:  Types of Decay |
 70%
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Some radioactive nucleus may emit

(1) Only one α,β or γ at a time

(2) All the three α,β and γ one after another

(3) All the three α,β and γ simultaneously

(4) Only α and β simultaneously

Subtopic:  Types of Decay |
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Which can pass through 20 cm thickness of the steel

(1) α particles                   

(2) β particles

(3) γ rays                         

(4) Ultraviolet rays

Subtopic:  Types of Decay |
 78%
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The half-life period of radium is 1600 years. Its average life time will be 
(a) 3200 years              (b) 4800 years
(c) 2319 years               (d) 4217 years

Subtopic:  Radioactivity (OLD NCERT) |
 73%
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What percentage of original radioactive atoms is left after five half lives 

(1) 0.3%               

(2) 1%

(3) 31%                 

(4) 3.125%

Subtopic:  Radioactivity (OLD NCERT) |
 79%
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Beta rays emitted by a radioactive material are

(1) Electromagnetic radiation

(2) The electrons orbiting around the nucleus

(3) Charged particles emitted by nucleus

(4) Neutral particles

Subtopic:  Types of Decay |
 66%
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Alpha rays emitted from a radioactive substance are

(1) Negatively charged particles

(2) Ionised hydrogen nuclei

(3) Doubly ionised helium atom

(4) Uncharged particles having the mass equal to proton

Subtopic:  Types of Decay |
 89%
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