Structure of Atoms

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option (iii) 1:3

The chlorine is a mixture of two isotopes with atomic masses 37U and 35U and its atomic mass is 35.5U. The atomic mass depicts that % composition of Cl-35 is much higher than that of Cl-37 and they are present in the ratio 1:3

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (i)

 “l” which is known as Azimuthal quantum number or orbital angular momentum or subsidiary quantum number depicts the three dimensional shape of the orbital.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  option (iii) 9

The total number of orbitals is given by n2, where n is the principal quantum number or the principal shell.

Thus for the third shell number of orbitals is 32 i.e. 9

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: (ii) Heisenberg's uncertainty principle.

According to Heisenberg's uncertainty principle it is impossible to determine simultaneously, the exact position and exact momentum (or velocity) of an electron. Thus it implies that determining the trajectory of an electron is impossible as it requires exact position and velocity which is not possible as per the uncertainty principle.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iii) 2

The number of angular nodes is given by n-l

where n is principal quantum number, l is azimuthal quantum number

For 4d orbital, n=4 and l=2

Thus, the number of angular nodes

 = n-l

 = 4-2

 = 2

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  option (iv)

The number of radial nodes is given by n-l-1

where n is principal quantum number, l is azimuthal quantum number

For 3p orbital, n=3 and l=1

Thus, the number of radial nodes

= n-l-1 

= 3-1-1

 = 1

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option (iv)

sum of the number of protons and neutrons is same but the number of protons is different

Isobars are the atoms which have same mass number (sum of number of neutrons and protons) but different atomic number (i.e. different proton number)

For example, ₁₄⁶C and ₁₄⁷N.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option (i)

Overall neutrality of atom.

According to the J.J Thomson model the positive charge is uniformly distributed and the electrons are embedded into it in such a manner as to give the most stable electrostatic arrangement just as watermelon of positive charge with plums or seeds (electrons) embedded into it. Thus this model is able to explain the overall neutrality of the atom

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option (ii)

The mass of an electron is equal to the mass of a neutron.

The neutron is heavier than the electron as

Mass of the neutron = 1.67 x 10^-27 kg

Mass of the electron = 9.11 x 10^-31kg

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (iv)

Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube. As per the result obtained from the cathode ray discharge tube experiment the characteristics of cathode rays (electrons) does not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube. Which concludes that electrons are the basic constituent of all the atoms