Question 1 :
Which of the following scientist identified the 'Atomic number' in the structure of an atom ?

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

Question 3 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2b2f59b460d7261f60c.JPG' /> Find out the valency of atoms represented by the figure.

Question 4 :
An atom with 3 protons and 4 neutrons will have a valency of

Question 5 :
One electron is present in the outer most shell of the atom of an element X. What would be the nature of charge on the ion formed if this electron is removed from the outermost shell ?

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

Question 7 :
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 8 :
The ratio of the radii of hydrogen atom and its nucleus is ~ $10^{5}$. Assuming the atom and the nucleus to be spherical, what will be the ratio of their sizes ?

Question 9 :
An element X has a mass number 4 and atomic number 2. Write the valency of this element?

Question 12 :
Which of the following correctly represent the electronic distribution in the Mg atom?

Question 13 :
Rutherford’s α-particle scattering experiment led to the discovery of the ____________.

Question 14 :
In the Gold foil experiment of Geiger and Marsden, that paved the way for Rutherford’s model of an atom, ~ 1.00% of the $\alpha$-particles were found to deflect at angles > $50^{\circ}$. If one mole of $\alpha$-particles were bombarded on the gold foil, compute the number of $\alpha$-particles that would deflect at angles less than $50^{\circ}$.

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 17 :
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 18 :
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 19 :
Which of the following correctly represent the electronic distribution in the Mg atom?

Question 20 :
Neon and chlorine have atomic numbers 10 and 17 respectively. Their valencies will be ______ and _______ respectively.