Question 2 :
Electrons are the kind of particles which revolve around the nucleus.

Question 6 :
In _________, J.J. Thomson discovered the electron, the first subatomic particle.

Question 10 :
According to J.J Thomson's atomic model, negative charges are embedded in:

Question 11 :
An atom of silicon has a mass number of $29$. How many neutrons does it have?

Question 12 :
By charging the metal electrodes and gas inside the cathode ray tube :

Question 13 :
The electrode connected to the negative terminal of a battery in a discharge tube is called ________.

Question 17 :
Though the three fundamental particles are present in almost all elements, one element does not have one of them. Identify the particle<br/>

Question 19 :
<span>If number of electrons in an atom is 8 and number of protons is also 8, then </span>give the atomic number of atom and the charge on the atom.<br/>

Question 21 :
If two atoms are isotopes, in what characteristic do they differ?

Question 23 :
Which of the following is true for mass and charge of electron?

Question 24 :
Assertion: <span>Metals are good conductors of heat and electricity.</span><br/> Reason: <span>The positive nuclei are surrounded by a &#34;sea&#34; of mobile electrons.</span>

Question 26 :
It was known by 1900 that the atom was not a............. , ................particle but contained at least one sub-atomic particle the electron identified by J.J. Thomson.

Question 28 :
<span>Match column A (name of the Scientists) with column B (their contributions towards the understanding of the atomic structure).</span><div><br/><table class="table table-bordered"><tbody><tr><td> Column A</td><td> Column B</td></tr><tr><td> A. Ernest Rutherford</td><td> 1. Indivisibility of atoms</td></tr><tr><td> B. J.J Thompson</td><td> 2. Stationary orbits</td></tr><tr><td> C. Dalton</td><td> 3. Concept of nucleus</td></tr><tr><td> D. Neils Bohr</td><td> 4. Discovery of electrons</td></tr><tr><td> E. James Chadwick</td><td> 5. Atomic number</td></tr><tr><td> F. E Goldstein</td><td> 6. Neutron</td></tr><tr><td> G. Moseley</td><td> 7. Canal rays</td></tr></tbody></table></div>

Question 29 :
Which of the following is used as neutron absorber in the nuclear reactor?

Question 32 :
Atoms of the same element possessing identical mass but differing in half-life period are called:<br/>

Question 33 :
When electric field is applied, the cathode rays bend towards :

Question 34 :
The purpose of electron gun in a cathode ray tube is :

Question 35 :
Assertion: $\alpha-$ rays have greater ionizing power than $\beta-$ rays. Reason: $\alpha-$ particles carry two unit positive charge while $\beta-$ particles carry only one unit negative charge.

Question 38 :
What is X in the nuclear reaction?<br>$_7N^{14} + _1H^1 \rightarrow _8O^{15} + X$

Question 39 :
The most effective bombarding particle (projectile) in the transmutation of a heavy element is:<br/>

Question 44 :
Alpha particles are positively charged and contains the nucleus of ________ atom.

Question 47 :
A and B are two elements which have same atomic weight and are having atomic number 27 and 30 respectively. If the atomic weight of A is 57 then number of neutron in B is :

Question 48 :
The nuclear activity of a neutral atom is always _____ when compared to its ion.

Question 49 :
If a radioactive element $_{79}{Au}$ emits $\beta$-particle, what is the new group? $_{79}{Au}$ belongs to group I B (copper family)?<br/>

Question 50 :
Which one is not concerned with the use of radio isotope?<br>

Question 53 :
$^{214}_{82} Pb \xrightarrow{- \beta} ^{214}_{83} A \xrightarrow{- \alpha} ^{210}_{81} B \xrightarrow{- \beta} ^{210}_{82} C \xrightarrow{\alpha} ^{206}_{80} D$<br/>The correct statement(s) is/are

Question 54 :
A sample of $U^{238} ((half\!-\! life = 4.5\times 10^9 \: yr)$ ore is found to contain 23.8 g of $U^{238}$ and 20.6 g of $Pb^{206}$. The age of the ore is :<br/>

Question 55 :
The activity of a radioactive isotope falls to $12.5\, \%$ in 90 days. The half life and decay constant of isotope are :

Question 56 :
A sample of $^{14}{CO_2}$ was mixed with ordinary $^{12}{CO_2}$ for studying a biological tracer experiment. The 10 mL of this mixture at STP possess the rate of $10^4$ disintegration per minute. The number of millicurie of radioactive carbon is needed to prepare 60 litre of such a mixture is :<br/>