Question 2 :
A cation with $+2$ charge with&#160;atomic number $56$ and atomic mass $137$ contains:<br/>I. $54$ protons<br/>II. $81$ neutrons<br/>III. $54$ electrons

Question 3 :
The number of electrons in an atom is equal to number of

Question 4 :
Which of the following statements about Rutherford&#8217;s model of atom are correct?<br/><br/>(i) considered the nucleus as positively charged.<br/>(ii) established that the $\alpha$&#8211;particles are four times as heavy as a hydrogen atom.<br/>(iii) can be compared to solar system.<br/>(iv) was in agreement with Thomson&#8217;s model.

Question 7 :
Consider the following species:<br/>$I:CO$ &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160;$II:NO$<br/>$III:N_2$ &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; $IV:HCHO$<br/><br/>Select species with equal number of neutrons, protons and electrons in each.&#160;

Question 8 :
Boron has two stable isotopes, $^{10}B (19\%)$ and&#160;&#160;$^{11}B(81\%)$. Average atomic weight for boron in the periodic table is:<br/>

Question 9 :
In an element, the number of protons, electrons and neutrons are $1$, $0$, $1$ respectively. Identify the element.

Question 11 :
The total number of protons, electrons and neutrons in 12 g of $^{12}_6C$ is equal to ________.<br/>

Question 12 :
An element X has a mass number 4 and atomic number 2. The valency of this element is:

Question 14 :
The number of electrons present in the valence shell of an atom with atomic number 38 is&#160;:

Question 16 :
An ion&#160;$\displaystyle M^{3+}$ contains 10 electrons and 14 neutrons Element M has valency equal to the valency of another element X which has five electrons less than Ar in its outermost shell Identify the elements M and X.

Question 17 :
State which of the following is correct :<br/>A neutral atom, atomic number 33 and atomic mass 75, contains :<br/>(1) 75 neutrons<br/>(2) 42 electrons<br/>(3) 33 protons

Question 19 :
Assertion: Two electrons in Helium are placed in only one shell while three electrons in Lithium occupy two shells. Reason: An orbit can have maximum $2n^2$ of electron so first orbital can have two electron only.

Question 20 :
Statement 1 : $\displaystyle Ca$ is a neutral atom.<br/>Statement 2 : It has the same number of protons and electrons.

Question 21 :
Which of the following elements has least number of electrons in its M shell?

Question 22 :
Which other element has the same number of valence electrons as aluminum?

Question 23 :
According to J.J. Thomson's atomic model, negative charges are embedded in :

Question 24 :
Given that the abundances of isotopes $^{54}Fe, ^{56}Fe$ and $^{57}Fe$ are $5\%, 90\%$and $5\%$respectively, the atomic mass of $Fe$ is:<br>

Question 25 :
Statement 1: The value of Avogadro's constant is $6.022\times {10}^{23}$<br/>Statement 2: Mole is the ratio of number of atoms present in the substance to the Avogadro number.<br/>Now choose the correct option :