Question 1 :
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 2 :
The number of electrons in an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of the element?

Question 3 :
Why did Rutherford select a gold foil in his $\alpha$–ray scattering experiment?

Question 4 :
Rutherford’s α-particle scattering experiment led to the discovery of the ____________.

Question 5 :
Helium atom has a valency of zero, even after having 2 electrons in its valence shell, because

Question 6 :
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 7 :
Which of the following scientist identified the 'Indivisibility of atoms' in the structure of an atom ?

Question 9 :
Which of the following scientist identified the 'Atomic number' in the structure of an atom ?

Question 10 :
In response to a question, a student stated that in an atom, the number of protons is greater than the number of neutrons, which in turn is greater than the number of electrons. Do you agree with the statement ? (Yes/No)

Question 12 :
Which of the following scientist identified the 'Stationary orbits' in the structure of an atom ?

Question 13 :
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 14 :
An element X has a mass number 4 and atomic number 2. Write the valency of this element?

Question 15 :
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 16 :
Which of the following correctly represent the electronic distribution in the Mg atom?

Question 17 :
Neon and chlorine have atomic numbers 10 and 17 respectively. Their valencies will be ______ and _______ respectively.

Question 18 :
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 20 :
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.