Atomic and Nuclear Structure

Question 1

Emission spectrum of hydrogen

Answer 1

• When an electron transitions from a higher energy level to a lower energy level, it emits electromagnetic radiation.
• The emission spectrum of hydrogen consists of sharp, distinct lines.

Question 2

Bohr Model

Answer 2

• An electron orbits the positively charged nucleus in the same way that the earth orbits the Sun.
• Electrostatic attraction pulls the electron toward the nucleus.
• The electron orbits at high speed to prevent it from crashing into the nucleus.
• The electron can orbit at different energy levels: n=1, n=2, n=3 …etc.
• The higher the energy level, the larger the radius from the nucleus.

Question 3

Higher atomic numbers indicate what type of binding energy?

Answer 3

Higher Z values give more negative binding energy (more stable) because the more charge, the more electrostatic attraction.

Question 4

What is the energy of the energy levels is governed by? (The equation)

Question 5

The more negative the energy, what does it mean?

Answer 5

The more negative (lower) the energy, the more stable the orbit, the harder it is to knock out the electron.

Question 6

The wavelength of the emitted or absorbed radiation is governed by the Rydberg formula

Answer 6

where R is the Rydberg constant 1.9 x 10⁷ m^-1

Question 7

The energy of the emitted or absorbed radiation is:

Question 8

When the final energy is lower than the initial energy, what happens to the energy? When the final energy is higher than the initial energy, what happens to the eenrgy?

Answer 8

• Energy is emitted for transitions to lower energy levels (nf < ni).
• Energy is absorbed for transitions to higher energy levels (nf > ni).

Question 9

Alpha Decay

Answer 9

Ejection of a helium nucleus at relatively low speed.

Question 10

Beta Decay

Answer 10

Ejection of a high speed electron.

Question 11

Gamma Decay

Answer 11

Release of high energy electromagnetic wave.

Question 12

Rank the strength of an alpha particle, beta particle, and gamma ray.

Answer 12

Alpha particle: Weakest form of radiation. Can be stopped by a sheet of paper. It is essentially a relatively low speed helium nucleus.

Beta particle: More energy than an alpha particle. Can be stopped by aluminum foil. It is a high speed electron.

Gamma ray: Strongest form of radiation. It is a high energy electromagnetic wave. Can be stopped by a thick layer of lead or concrete.

Question 13

Relate stability to half-life

Answer 13

• When something is stable, it doesn’t decay.
• When something is unstable, it decays.
• The more unstable something is, the shorter the half-life.

Question 14

What is the mathematical expression for half-life?

Question 15

General nature of fission

Answer 15

• Fission = one nuclei splitting apart.
• Uranium undergoes fission when struck by a free neutron.
• The fission of uranium generates more neutrons, which goes on to split other Uranium nuclei. This is called a chain reaction.

Question 16

General nature of fusion

Answer 16

• Fusion = two nuclei coming together.
• The Sun works by fusion.
• Hydrogen in the Sun fuses to form helium.

Question 17

The energy that makes up for the mass deficit is calculated by

Question 18

Binding energy per nucleon is highest and lowest for:

Answer 18

• Binding energy per nucleon is strongest for Iron (Fe 56).
• Binding energy per nucleon is the weakest for Deuterium (the 2-nucleon isotope of hydrogen).