Unit 3: Part 2 of the Atom Nuclear Chemistry
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the Atom Nuclear Chemistry I. The Nucleus I. The Nucleus (p. 701 – 704 in Class Modern Chemistry Text) I IV III II
description
Unit 3: Part 2 of the Atom Nuclear Chemistry. I. The Nucleus (p. 701 – 704 in Class Modern Chemistry Text). I. II. III. IV. A. Mass Defect. Difference between the mass of an atom and the mass of its individual particles. 4.00260 amu. 4.03298 amu. Important Values. - PowerPoint PPT Presentation
Transcript of Unit 3: Part 2 of the Atom Nuclear Chemistry
Unit 3: Part 2 of the Atom
Nuclear
Chemistry
Unit 3: Part 2 of the Atom
Nuclear
ChemistryI. The NucleusI. The Nucleus(p. 701 – 704 in Class
Modern Chemistry Text)
I. The NucleusI. The Nucleus(p. 701 – 704 in Class
Modern Chemistry Text)
I
IV
III
II
A. Mass DefectA. Mass DefectA. Mass DefectA. Mass Defect
Difference between the mass of an atom and the mass of its individual particles.
4.00260 amu 4.03298 amu
Important ValuesImportant Values
1.007276 amu = mass of 1 p+
1.008665 amu = mass of 1 n0
0.0005486 amu = mass of 1 e-
1.6605 x 10-27 kg = 1 amuSpeed of light (c) = 3.00 x 108 m/s
A. Mass Defect A. Mass Defect CalculatedCalculatedA. Mass Defect A. Mass Defect CalculatedCalculated
Helium-4 nuclide: Atomic Mass = 4.002602 amu
How do we calculate its mass defect? Find the mass of the subatomic particles 1st
2 p+ = (2 x 1.007276 amu) = 2.014552 amu 2 n0 = (2 x 1.008665 amu) = 2.017330 amu 2 e- = (2 x 0.0005486 amu) = 0.001097 amu Total combined mass = 4.032979 amu
A. Mass Defect A. Mass Defect CalculatedCalculatedA. Mass Defect A. Mass Defect CalculatedCalculated
How do we calculate its mass defect?Total combined mass - Atomic mass = mass defect4.032979 amu – 4.002602 amu = 0.030377 amu
The measured mass is 0.030377 amu less then the total mass we calculated for the combined subatomic particles
This is the mass defect for the helium-4 nuclide
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
Energy released when a nucleus is formed from nucleons.
High binding energy = stable nucleus.
E = mc2E: energy (J)m: mass defect (kg)c: speed of light
(3.00×108 m/s)
Converting mass defect to Nuclear Binding Energy
Converting mass defect to Nuclear Binding Energy
We will use the helium-4 nuclide again1. Convert mass defect from amu to kg
0.030377amu 1.6605 x 10-27 kg 1 amu
2. E = mc2 = (5.0441x10-29 kg)(3.00 x 108 m/s)2 = 4.54 x 10-12 J
This is the energy required to hold the nucleus together
= 5.0441x10-29
kg
Practice ProblemPractice Problem
Calculate the nuclear binding energy of a sulfur-32 atom. The measured atomic mass of this nuclide is 31.972070 amu.
Answer = 4.36 x 10-11 J
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
B. Nuclear Binding B. Nuclear Binding EnergyEnergy
Unstable nuclides are radioactive and undergo radioactive decay.
Nuclear ReactionsNuclear ReactionsNuclear ReactionsNuclear Reactions
In equations representing nuclear reactions, the total of the atomic numbers and the total of the mass numbers must be equal on both sides of the equation.
Here is an example
Br + He C + n
Notice there has been a transmutation
94
42
126
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radioactive decay nuclear fusion a chain reaction nuclear fission radiocarbon dating
A process in which a very heavy A process in which a very heavy nucleus splits into more-stable nucleus splits into more-stable nuclei of intermediate mass is nuclei of intermediate mass is
called:called:
A process in which a very heavy A process in which a very heavy nucleus splits into more-stable nucleus splits into more-stable nuclei of intermediate mass is nuclei of intermediate mass is
called:called:
Quiz
QuizQuizQuizQuizVery large nuclei tend to be unstable
because of the: repulsive forces between protons attraction of protons for neutrons repulsive forces between neutrons attraction of electrons for the positively
charged nucleus
QuizQuizQuizQuiz
Compared to chemical reactions, nuclear reactions produce: proportionally far less energy proportionally far more energy more vegetables fewer changes in the nucleus
Online practice quiz for you to try
Using the Modern Chemistry text try the section review questions on page 704.
http://www.sciencegeek.net/Chemistry/
taters/Unit1NuclearChemistry.htm http://www.sciencegeek.net/Chemistry/
taters/Unit1NuclearChemistry.htm
VOCABULARYVOCABULARYVOCABULARYVOCABULARY Nucleons: the protons and neutrons in the nucleus of
an atom Nuclide: an atom in nuclear chemistry is referred to
as one of these Mass defect: the difference between the mass of an
atom and the sum of the masses of its protons, neutrons, and electrons
Nuclear binding energy: the energy released when a nucleus is formed from nucleons. It is calculated using E = mc2
Nuclear reaction: a reaction that changes the nucleus of an atom
transmutation: a change in the identity of a nucleus as a result of a change in the number of protons
