Question 1 :
Which of the following scientist identified the 'Concept of nucleus' in the structure of an atom ?

Question 2 :
Identify the $Mg^{2+}$ ion from the figure where, n and p represent the number of neutrons and protons respectively.

Question 3 :
The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. What is the name given to such a pair of elements?

Question 6 :
Which of the following scientist identified the 'Electrons' in the structure of an atom ?

Question 7 :
Rutherford’s 'alpha ($\alpha$) particles scattering experiment’ resulted in to discovery of _______.

Question 9 :
Rutherford’s $\alpha$–particle scattering experiment showed that (i) electrons have negative charge (ii) the mass and positive charge of the atom is concentrated in the nucleus (iii) neutron exists in the nucleus (iv) most of the space in atom is empty Which of the above statements are correct?

Question 10 :
The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

Question 11 :
In a sample of ethyl ethanoate ($CH_{3}COOC_{2}H_{5}$) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?

Question 12 :
In the Thomson’s model of atom, which of the following statments are correct? (i) the mass of the atom is assumed to be uniformaly distributed over the atom (ii) the positive charge is assumed to be uniformaly distributed over the atom (iii) the electrons are uniformaly distributed in the positively charged sphere (iv) the electrons attract each other to stabilise the atom.

Question 13 :
Which of the following is true for an element? (i) Atomic number = number of protons + number of electrons (ii) Mass number = number of protons + number of neutrons (iii) Atomic mass = number of protons = number of neutrons (iv) Atomic number = number of protons = number of electrons.

Question 14 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2b1f59b460d7261f60a.JPG' /> Which of the above in the figures do not represent Bohr's model of an atom correctly?

Question 15 :
Which of the following scientist identified the 'Stationary orbits' in the structure of an atom ?

Question 16 :
Which of the following scientist identified the 'Neutron' in the structure of an atom ?

Question 17 :
Which of the following scientist identified the 'Canal rays' in the structure of an atom ?

Question 18 :
Why did Rutherford select a gold foil in his $\alpha$–ray scattering experiment?

Question 19 :
In the atom of an element X, 6 electrons are present in the outermost shell. If it acquires noble gas configuration by accepting requisite number of electrons, then what would be the charge on the ion so formed?

Question 20 :
Atomic models have been improved over the years. Arrange the following atomic models in the order of their chronological order (i) Rutherford’s atomic model (ii) Thomson’s atomic model (iii) Bohr’s atomic model