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Nuclear Chemistry-Random Sources
Chem Book
28
Chemistry
Undergraduate 1
10/27/2013

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Cards

Term
Ways to Characterize a Nucleus
Definition
Atomic Number (Z)
Mass Number (A)
Size
Shape
Binding Energy
Angular Momentum
Half-Life (if unstable)
Term
What is
"Nuclear Binding Energy"?
Definition
The energy which holds a nucleus together.

or

The energy required to split a nucleus up into its constituents.
Term
Define "Half-Life"
Definition
The time required for half of the population of a group of unstable nucelei to decay.

Rate of decay is related to the mean lifetime of a decaying nucleus.

Can vary from billions of years to a tiny fraction of a second.
Term
Define "Isotope"
Definition
A nucleus with the same Z (number of protons) but a different A (different atomic mass, which means different number of neutrons).
Term
Define Isobar
Definition
A nucleus with different Z but the same number of A (atomic mass).
Term
Would the chemical properties of isotopes be more different or more similar?
Definition

More similar.

 

This is because: Chemistry is the study of the interactions between protons and electrons.

Thus with the same number of protons and electrons present, chemically speaking, isotopes will behave very similarly to each other.

Term
What are the three isotopes of Hydrogen?
Definition
Hydrogen (No neutrons)
Deuterium (1 Neutron)
Tritium (2 Neutrons, unstable)
Term
Is the mass of an atom more or less than the sum of the individual masses of it's constituents?
Definition
Less.

Energy is given off when
Term
How does binding energy relate to the number of protons and neutrons in a nucleus?
Definition
Binding energy generally continues to grow as more nucleons are added to the nucleus.

This is true until roughly about A= 60, at ~8 MeV per nucleon.

Past A=60 the binding energy starts to decrease slowly up to the most massive nuclei, which have energy around 7 MeV.
Term
List Three Important Nuclear Models
Definition
Liquid Drop Model
The Shell Model
The Collective Model
Term
Generally speaking, the conflict between what forces limits the ability of a nucleus to grow?
Definition
The balance between the electromagnetic force and the nuclear forces create a limit.
Term
What is the general goal of nuclear physics?
Definition
To account for the properties of nuclei in terms of mathematical models of their structures and internal motion.
Term
What is the ratio of the nucleus to the total diameter of an atom?
Definition
1/100000
Term
Define a "Nuclide".
Definition
A specific nucleus defined by the number of protons (the atomic number) and neutrons present.

More generally each have a specific nucleon number (atoms mass)
Term

Practice Question: 

A nuclide that has 26 protons and 33 neutrons is used to study blood chemistry.

 Write its nuclide symbol in the form of ZAX

  What are two other ways to represent this nuclide?

Definition

Because this nuclide has 26 protons, its atomic number, Z, is 26, identifying the element as iron, Fe.

 

This nuclide of iron has 59 total nucleons (26 protons + 33 neutrons), so its nucleon number, A, is 59.

 

5926Fe

 59Fe

 iron-59

Term
Which two forces act upon the nucleus and help produce it's structure?
Definition
The electrostatic (electromagnetic) and strong force.
Term

For lighter elements, having an even proton to neutron ratio is suffice to keep a stable nucleus. 

For heavier elements does this trend stay the same, that is, is an even number of protons to neutrons enough to keep the nucleus stable?

 

If not then how does it change? 

Definition

No.

For heavier elements, more neutrons than protons start to become necessary.

This is because with the higher number of protons, the electromagnetic repulsion between grows, and more neutrons per protons are needed in order to compensate (with the strong force). 

Term
Do nuclei exist that have no neutrons and more than one proton?
Definition

No, the electrostatic repulsion between the protons makes any such arrangements impossible. 

The neutrons are needed to help stabilize a nucleus. 

Term
How many naturally occuring stable nuclei are there?
Definition

264 

Known, naturally occuring, stable nuclei. 

Term

Describe the "Band of Stability"

 

Definition

Band of Stability

-Is is an area on a graph of protons to neutrons in which stable nuclei are found.

-A nuclide found outside of this band will likely undergo one or more nuclear reactions (radioactive decay) to make it fall into this band of stability.

-The band stops at 83 protons, but scientists postulate that around 114 protons and 184 neutrons should be an "island of stability".

[image]

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Term
Isotopes occurring above and to the left of the band of stability tend to emit what, and why?
Definition
-Beta emitters.
-Because they want to lose a neutron and gain a proton.
Term
Those lying below and to the right of the band of stability tend to emit what, and why?
Definition
-Positron emitters
-Because they want to lose a proton and gain a neutron.
Term
Isotopes above element 83 tend to emit what type of particle?
Definition
-Alpha Particle
-Because they have too many nucleons.
Term
Describe the "Odd-Even" Rule.
Definition
When the numbers of neutrons and protons in the nucleus are both even numbers, the isotopes tends to be far more stable than when they are both odd.
Term
What is the source of the "Odd-Even" Rule?
Definition
Has to do with the spins of nucleons (both have spin).
-When two protons or neutrons have paired spins (opposite spins), their combined energy is less than when they are unpaired.
Term
Briefly describe what the "Magic Number" rule states.
Definition
Isotopes with certain numbers of protons or neutrons tend to be more stable then the rest.
Term
What are the magic numbers of protons?
Definition
2, 8, 20, 28, 50, 82, 114
Term
What are the magic numbers of neutrons?
Definition
2, 8, 20, 28, 50, 82, 126, 184
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