brodidit for students
Atomic and nuclear physics
NET · Physics · 5 questions
Name: ____________________ Date: ____________
What is the energy of the electron in the ground state of the hydrogen atom?
- A -3.4 eV
- B -13.6 eV
- C +13.6 eV
- D 0 eV
The transition of an electron in hydrogen from n = 3 to n = 2 belongs to which series?
- A Lyman
- B Balmer
- C Paschen
- D Brackett
A radioactive sample has a half-life of 10 days. What fraction is left after 30 days?
- A 1/9
- B 1/6
- C 1/3
- D 1/8
Which particle is neutral and has a mass close to that of a proton?
- A Electron
- B Neutron
- C Positron
- D Neutrino
How many neutrons are in a nucleus of uranium-235? (Atomic number 92)
- A 92
- B 235
- C 143
- D 327
Answer key
1. B, 2. B, 3. D, 4. B, 5. C
In the Bohr model the ground state energy of hydrogen is -13.6 eV.
Transitions ending at n = 2 form the Balmer series, which lies partly in the visible region.
30 days is three half-lives, so the fraction left is (1/2)³ = 1/8.
The neutron carries no charge and has almost the same mass as the proton.
Neutrons = mass number - atomic number = 235 - 92 = 143.