QJEEM21Chcaf5: JEE Main 2021 Chemistry - Class 11 JEEM21Chcaf5 Solution: According to Bohr's atomic theory : (A) Kinetic energy of…

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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 :

Accepted Answer

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)

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