Question

The total energy of the electron in the first excited state of hydrogen is$-3.4\mathrm{eV}$. What is its kinetic energy?

• A. $+3.4$ $\mathrm{eV}$
• B. $+4.3$ $\mathrm{eV}$
• C. $+6.3\mathrm{eV}$
• D. $+7\mathrm{eV}$

Answer 1

The correct option is A

$+3.4$ $\mathrm{eV}$

Explanation for the correct option:

(A)$+3.4$$\mathrm{eV}$

• Total Energy of an excited electron $=$$[-]$Kinetic Energy of the electron in that excited state.
• So, T.E $=$[$-$]K.E
• Therefore, If T.E$=$$-3.4$$\mathrm{eV}$
• Then, K.E$=$$-$[$-$]$3.4$$\mathrm{eV}$
• Hence, K.E$=+$$3.4$$\mathrm{eV}$

So, option (A) is correct.

Explanation for the incorrect options

Since, the correct value of kinetic energy is $+3.4$ $\mathrm{eV}$. Therefore, the options (B), (C) and (D) are incorrect.

Hence, option (A)$+3.4$$\mathrm{eV}$ is the Kinetic Energy of the electron.