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Chapter 4. The Atom – Part 2. Subatomic Particles. Alchemy “The Golden Rule”. The number of protons in the nucleus of the atom ( atomic number = Z ) determines the atoms identity. Gold Atom Lead Atom. Mass Number. The sum of the protons and neutrons in the nucleus of an atom.

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Chapter 4

Chapter 4

The Atom – Part 2




The number of protons in the nucleus of the atom atomic number z determines the atoms identity
The number of protons in the nucleus of the atom (atomic number = Z) determines the atoms identity

Gold Atom Lead Atom


Mass number
Mass Number

  • The sum of the protons and neutrons in the nucleus of an atom.



Carbon 12
Carbon - 12

  • This is the symbol for the isotope carbon-12.

  • Atomic number is 6.

  • Mass number is 12.


Isotopes
Isotopes

  • Isotopes are different types of atoms of a chemical element, having the same number of protons in the nucleus, but having different numbers of neutrons in the nucleus.

  • Isotopes therefore have the same atomic number but different mass numbers.

  • There are 275 isotopes of the 81 stable elements, in addition to over 800 radioactive isotopes, and every element has known isotopic forms.

  • Isotopes of a single element possess almost identical properties.



Carbon 121
Carbon - 12

  • Write the symbols for carbon-13 and carbon-14.



Atomic mass
Atomic Mass

  • The atomic mass of carbon is 12.01 amu.

  • Atomic mass is the average mass of all the isotopes of an atom. It takes into account the different isotopes of an element and their relative abundance.


What is the average atomic weight for chlorine if it has two isotopes? The percent abundance for chlorine-35 is 75.53%. The percent abundance for chlorine-37 is 24.40%. The mass for Cl-35 is 35.0 amu and for Cl-37 it is 37.0 amu.

[(0.7553)(35.0 amu)] + [(0.2440)(37.0 amu)]

= [26.4355] + [9.028]

= 35.4635

the atomic weight of Cl= 35.5 amu


What is the average atomic mass for thallium, Tl? The two stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .

204.5 amu


What is the average atomic mass for thallium, Tl? The two stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .

[(0.7048)(205.059 amu)] + [(0.2952)(203.059 amu)]

= [144.5256] + [59.943]

= 204.4686

the atomic weight of Tl = 204.5 amu


Common uses of isotopes
Common Uses of Isotopes stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .

  • Isotope Analysis

  • Radiometric Dating

  • Nuclear Medicine:

    • Magnetic Resonance Imaging (MRI)

    • Positron Emission Tomography (PET scans)


Importance of isotopes
Importance of Isotopes stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .


Radiometric Dating stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .


Half life
Half-Life stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .

  • The decay of radioactive elements occurs at a fixed rate.

  • The half-life of a radioactive isotope is the time required for one half of the material to degrade into a more stable material.

  • Although the half-life pattern is the same for every radioactive isotope, the length of a half-life is different.

  • For example, C-14 has a half-life of about 5730 years while Ir-192 has a half-life of about 74 days.


Half life1
Half-Life stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .


Carbon dating
Carbon Dating stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .


Nuclear Medicine stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % . refers to imaging techniques that use radioactive isotopes to detect and treat disease. Magnetic resonance imaging (MRI) and positron emission tomography (PET scans) are examples.


Mri pet scan
MRI PET scan stable isotopes and their abundances are listed here.Tl-205 has a mass of 205.059 amu with an abundance of 70.48 % and Tl-203 has a mass of 203.059 amu with an abundance of 29.52 % .






How many electrons, protons and neutrons are in an atom of actinium with a mass number of 221?

89p+

89e-

132n0



Homework
Homework rhodium-105?

  • Chapter 4 Worksheet 1


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