The energy of electron in first excited state of `H`-atom is `-3.4 eV` its kinetic energy is

Options

A. `-3.4 eV`
B. `-6.8 eV`
C. `6.8 eV`
D. `3.4 eV`

Answer

D

Explanation

Kinetic energy of electron
`K = (Ze^(2))/(8pi epsilon_(0)r)`
Potential enegry of electron `U =- (1)/(4pi epsilon_(0)) (Ze^(2))/(r )`
`:.` Total energy
`E = K + U = (Ze^(2))/(8pi epsilon_(0)r) - (Ze^(2))/(4pi epsilon)`
or `E=- (Ze^(2))/(8pi epsilon_(0)r)`
or `E =- K`
or `K =-E =- (-3.4) = 3.4 eV`