Question

A hydrogen - like atoms has one electron revolving around a stationary nucleus. The energy required to excite the electron from the second orbit to the third orbit is 47.2 eV. The atomic number of the atom is:

• A. 3
• B. 4
• C. 5
• D. 6

Answer 1

The correct option is C 5

According to the question, $47.2=13.6Z^2(\frac{1}{2^2}-\frac{1}{3^2})$
Solving we get $z=5$.