JEE MAIN - Chemistry (2021 - 24th February Evening Shift - No. 4)
According to Bohr's atomic theory :
(A) Kinetic energy of electron is $$ \propto {{{Z^2}} \over {{n^2}}}$$.
(B) The product of velocity (v) of electron and principal quantum number (n), $$'vn' \propto {Z^2}$$.
(C) Frequency of revolution of electron in an orbit is $$ \propto {{{Z^3}} \over {{n^3}}}$$.
(D) Coulombic force of attraction on the electron is $$ \propto {{{Z^3}} \over {{n^4}}}$$.
Choose the most appropriate answer from the options given below :
(A) Kinetic energy of electron is $$ \propto {{{Z^2}} \over {{n^2}}}$$.
(B) The product of velocity (v) of electron and principal quantum number (n), $$'vn' \propto {Z^2}$$.
(C) Frequency of revolution of electron in an orbit is $$ \propto {{{Z^3}} \over {{n^3}}}$$.
(D) Coulombic force of attraction on the electron is $$ \propto {{{Z^3}} \over {{n^4}}}$$.
Choose the most appropriate answer from the options given below :
(A), (C) and (D) only
(A) only
(C) only
(A) and (D) only
Explanation
According to Bohr's theory,
I. $$KE \propto {{{Z^2}} \over {{n^2}}}$$ or $$13.6 \propto {{{Z^2}} \over {{n^2}}}{{(eV)} \over {(atom)'}}$$
($$\therefore$$ Correct)
II. Speed of electron $$ \propto {Z \over n}$$
(Here, Z = atomic number, n = number of shells)
$$\therefore$$ $$v \times n \propto Z$$ ($$\therefore$$ Incorrect)
III. Frequency of revolution of electron $$ = {v \over {2\pi r}}$$
Frequency $$ \propto {{{Z^2}} \over {{n^3}}}$$ ($$\because$$ $$v \propto {z \over n},r \propto {{{n^2}} \over z}$$) ($$\therefore$$ Incorrect)
I. $$KE \propto {{{Z^2}} \over {{n^2}}}$$ or $$13.6 \propto {{{Z^2}} \over {{n^2}}}{{(eV)} \over {(atom)'}}$$
($$\therefore$$ Correct)
II. Speed of electron $$ \propto {Z \over n}$$
(Here, Z = atomic number, n = number of shells)
$$\therefore$$ $$v \times n \propto Z$$ ($$\therefore$$ Incorrect)
III. Frequency of revolution of electron $$ = {v \over {2\pi r}}$$
Frequency $$ \propto {{{Z^2}} \over {{n^3}}}$$ ($$\because$$ $$v \propto {z \over n},r \propto {{{n^2}} \over z}$$) ($$\therefore$$ Incorrect)
Comments (0)
