Question 2 :
Mass of one twelth of carbon atom is called atomic mass unit.<br/><br/>

Question 3 :
Which of the following pair below represents isotopes of the same element?

Question 4 :
The isotopes present in naturally occurring uranium are<br><br>$(i)$ <br> $U-235$<br>$(ii)$ <br> $U-236$<br>$(iii)$ <br> $U-238$<br>$(iv)$ <br> $U-232$<br>

Question 5 :
Which of the following isotopes is likely to be most stable ?

Question 7 :
An atom contains 12 protons, 12 electrons, and 13 neutrons.<br>Which of the following combinations of particles is an isotope of that atom?<br>

Question 9 :
Which of the following is true for the following isotopes of uranium<br/><br/>U$^{235}$ and U$^{238}$?

Question 10 :
Assertion: Density of all the nuclei is same. Reason: Radius of nucleus is directly proportional to the cube root of mass number.

Question 12 :
An element A decays into an element C by a two-step process:<br>$A\rightarrow B+He_2^4$ and $B\rightarrow C+{ 2e }_{ -1}^{ 0 }$.Then<br>

Question 13 :
How many grams are there in a $7.0$ mol sample of sodium hydroxide?

Question 15 :
An atom which has a mass number of 14 and has 8 neutrons is an:

Question 16 :
Though three fundamental particles are present in almost all elements. One element does not have&#160;:

Question 17 :
The notation for an isotope of sodium $^{23}_{11}Na$. Which row gives the composition of a neutral atom of this isotope of sodium?<table class="wysiwyg-table"><tbody><tr><td><br></td><td>number of protons</td><td>number of neutrons</td><td>number of electrons</td></tr><tr><td>A</td><td>$11$</td><td>$12$</td><td>$11$</td></tr><tr><td>B</td><td>$11$</td><td>$12$</td><td>$12$</td></tr><tr><td>C</td><td>$11$</td><td>$23$</td><td>$11$</td></tr><tr><td>D</td><td>$12$</td><td>$11$</td><td>$12$</td></tr></tbody></table>

Question 18 :
The $\beta$ -decay of $_{11} \ Na^{24}$ produces an isotope of:

Question 19 :
The equivalent weights of a metal are $18.66$ and $28$, then atomic weight of metal may be?

Question 20 :
The atomic mass of a hypothetical element X is 33.42 amu. A 27.22 g sample of X&#160;combines with 84.10 g of another hypothetical element Y to form the compound XY.&#160;The atomic mass of Y is:

Question 21 :
How many neutrons does the most common isotope of hydrogen have?

Question 22 :
Parto of the uranium decay series is shown<br/>$_{92}U^{238} \rightarrow _{90}Th^{234} \rightarrow _{91}Pa^{234}\rightarrow$ <br> $_{92}U^{234} \rightarrow _{90}Th^{230}\rightarrow _{88}Ra^{226}$<br/>How many pairs of isotopes are there in the above series :<br/>

Question 23 :
A beam of $16 MeV$ deutrons from a cyclotron falls on a copper block. The beam is equivalent to a current of 15$\mu A$. At what rate do the deutrons strike the block?

Question 24 :
X, Y, and Z are three atoms belonging to the same element. The atoms have mass numbers in the order X &lt; Y &lt; Z. They differ in their number of neutrons by one unit and they exist in the ratio of 1 : 1 : 2. What is the average atomic mass of this element if the atomic mass of the lightest isotope is A?