Download 2.10 Basic Nuclear Chemistry

Unit 2: Structure of Matter
Content Outline: Nuclear Chemistry Basics (2.10)
I.
Nuclide
A. This term refers to the nucleus of an atom. It is without the electron cloud.
B. Nucleons
1. This term refers to the components of an atom’s nucleus – protons & neutrons.
2. Remember, each proton and neutron has a mass = 1 AMU or Dalton; protons carry a positive
charge and neutrons carry no charge (neutral).
C. Nuclides can be written 2 ways:
1. Hyphen notation – the name followed by the Atomic mass. For example, Radium-228
2. Nuclear notation – Atomic mass over Atomic Number followed by Symbol.
For example, 22888 Ra
D. Nuclear Force
1. Short-range attractive forces that help hold together the nucleus of an atom.
A. Nuclear Binding Energy This term refers to the very small amount of energy that is released when
a nucleus is formed from nucleons.
B. This term can also refer to the energy required to break apart a nucleus.
C. The general trend is: as the nucleus increases in size and number of nucleons, the nuclear binding
energy increases until Iron (Fe). After Iron, the nuclear binding energy decreases due to the
nucleus being so large.
II. Nucleus Stability
A. Nuclear Shell Model
1. Nucleons exist in different energy levels/shells within the nucleus, just like electrons in the cloud.
2. Even numbers tend to be more stable than odd numbers of nucleons.
B. As the number of protons in a nucleus increases, the stability of the nucleus decreases
1. This is because the positive repulsive forces are greater than the Nuclear Force.
2. To reduce this instability, neutrons are needed to increase the distance between protons and
decrease the repulsive forces between protons.
a. This makes the Nuclear Force greater than the repulsive force.
C. Beyond Bismuth (Bi) with Atomic Number of 83, the repulsive forces are so great that there is no
Nuclear force and each atom is unstable and radioactive.
III. Marie and Pierre Curie (1896)
A. The Curie’s were a husband and wife team of French Physicists.
B. Marie Curie was the first woman to win a Nobel in Prize in 1903 for her work on radioactivity. She
later won a second Nobel Prize in 1911. She is the only female to win 2 Nobel Prizes. That is
awesome! Kinda like Alabama winning back-to-back National Championships.
C. Radioactive Decay
1. This is defined as the spontaneous disintegration (falling apart) of a nucleus into a smaller and
lighter (AMUs) by emitting (releasing) particles, electromagnetic radiation, or both.
D. Nuclear Radiation
1. This refers to particles or electromagnetic radiation emitted from the nucleus during radioactive
decay.
E. Radioactive Nuclide
1. Refers to an unstable, radioactive nucleus of an atom.
IV. The types of radioactive decayA. If you change the Atomic Number you change the element. This is known as a transmutation. So you
need a Periodic Table.
B. Alpha Particle Emission (α) or (42He) 1. This is the emission (release) of 2 protons and 2 neutrons as an alpha particle.
2. This causes the Atomic Number to decrease by 2 and the Atomic Mass to decrease by 4 AMUs.
3. This is the weakest penetrating radiation. (A couple sheets of paper can stop it.)
C. Beta Emission (β) or (0-1β)
1. This is when a neutron is converted to a proton and an electron. The electron is emitted from
the nucleus.
2. The Atomic Number increases by 1, but the Atomic Mass remains the same in AMUs.
3. This has greater penetrating strength than Alpha particle emission.
D. Positron Emission (0+1β)
1. This is when a proton is converted to a neutron and a positron. The positron is emitted.
a. Positron is a particle with the same mass as an electron, but possessing a positive charge.
b. The Atomic Number decreases by one, but the atomic mass remains the same in AMUs.
E. Electron Capture
1. An innermost electron is captured by the nucleus and combines with a proton to create a
neutron.
2. The atomic number decreases by 1, but the Atomic Mass remains the same in AMUs.
F. Gamma Emission (γ)
1. This is high energy electromagnetic radiation that is emitted as a nucleus goes from an excited
state to a ground state
a. This is similar to electrons emitting photons as the go from an excited to ground state.
b. The nuclear shell is emitting energy.
2. This is the most penetrating form of radiation. (It can penetrate lead.)
V. Writing and Balancing Nuclear Reactions
Example:
94Be
OR
21284
A.
B.
C.
D.
+ 42 He  126C + 10n Beryllium -9 + Alpha Particle yields Carbon-12 + 1 Neutron
Po  42 He + 20882 Pb
Step 1: Write in nuclear notation the element that is a reactant.
Step 2: Write in nuclear notation the type of radiation that is a reactant, if adding.
Step 3: Add or subtract the Atomic Masses (top number).
Step 4: Add or subtract the Atomic Number (bottom number) and then use the Periodic Table to find the
new element.
E. Step 5: Write in nuclear notation the new element as a product on the right side of the arrow.
F. Step 6: Write in nuclear notation the other remaining particle on the product side.