Tuesday, October 24, 2006


Lesson Title: Isotopes

Learning Outcome:At the end of the sessions, you must be able to define isotopes, cite the relationship between atomic mass and the relative abundance of isotope identify the use of some radioactive elements/isotopes

Learning Presentation:

What is an isotope? click here to find out you can also check you text books its on page 64-65 :)

or play this video for better understanding

From our previous lessons the atomic mass is the number of protons plus the number of neutrons but why are the mass in the periodic table of elements not in whole number is it because of the electrons?

The answer is no, it is not in whole numbers because it is the average mass of the isotopes present of that element to know how to calculate click here

1. The protons and neutrons are particles of the nucleus. The American physicist A. J. Dempster and the English chemist F. W. Anston (1914) found out that some elements have atoms with different atomic masses. These are called isotopes of the element. Atoms of the same element would have the same atomic number. The atomic mass of isotopes varies because they have different numbers of neutrons. Atomic mass is given by the sum of the masses of p+ and no present in the atom. Mass number is rounded off for convenience

1. The variation in the number of neutrons does not change the identity and therefore, the properties of an element. It is atomic number or the number of protons that identifies an element.

2. Atomic mass is generally, not a whole number. It is the weighted average of the masses of isotopes of a particular element. The percentage of isotopes of a particular element. The percentage abundance of each isotope is taken into account.

3. Isotopes are classified as stable and unstable.
a. Stable isotopes do not exhibit radioactivity, which explains why they exist and persist in nature. Many elements that occur naturally and abundantly on earth are stable isotopes. 16O and 12C are examples.

b. Unstable isotopes exhibit radioactivity (tremendous emission of invisible rays due to the splitting of the nucleus of an atom) and thus, are known as radioisotopes.

4. Using the unstable isotopes/radioisotopes
a. Dating fossils and rocks - Geologists use radioactive decay rates to tell the ages of rocks and fossils. Uranium –238 is used to determine the age of rocks. It takes 4.5 x 109 years for half of the sample of U-238 to decay.

b. Radiocarbon dating - This method is used to determine the ages of materials, which were once living. It is based on the decay rate of carbon-14. Living organisms contain an almost fixed amount of carbon-14 per unit mass. When the organisms die, C-14 starts to decay according to the rate law. The half-life of C-14 is 5730 years.

c. Medical uses - Radioisotopes are used to detect and treat abnormalities in the body.

Activity: click here to practice on a game

Application/ Valuing Assignment:
Answer the following by posting your answer or write on a piece of paper you will be graded based on the following
1. Give 2 or 3 examples of elements with isotopes which isotope is beneficial and how and which are not beneficial and why?
2. What is the impact of isotopes to our lives?
3. What are the biological effects of radiation?
4. What is the difference between natural and artificial radioactivity?
5. Can both be utilized to be beneficial to man?


  • At 2:59 AM, Blogger grinline21 said…

    Daniel Barenboim is different from his contemporaries in the sense that he is the only maestro who is making music for peace. His main goal in his line of interest is not only to become famous and great but to promote order and peace among nations specifically in the middle east. I could really say why he is totally different from the rest of the musicians in the world because of his natural born talent, inexplicable expertise, invaluable wisdom, infinite braveness, true fellowman and above all a noble and GOd fearing individual. He is superb, all aspects. Thats what makes this person a truly great performer....for his music includes great ideas about how should people live happily, unified in this world.

    It's not only in politics where you can share great ideas about how to live and how we should live in this world where competition is high, I should say. Every now and then, arguments are always around. To this it is just right for us to share little things that could be benefited by our fellowmen in a justified way through our own iniative by making use of our talents. So, Daniel Barenboim is justified in what he is doing - using music to address socio-political issues in the sense that it is this way where he can help and contribute solutions to the problems around the world in general. He is just being brave and intelectually impressive in his world where he managed to survive. Being a performer, a're just as great and brilliant as you are through what you can actually share to the people. For Daniel Barenboim, not just the music...but most importantly the message of his composition....funnelling ideas to the listeners which would lead them to reflection. Thus, promoting PEACE and UNITY in the hearts and minds of the individuals.

    If he was in the Philippines, the similar issues I think he would address are our problems in the government in general. To mention, graft and corruption and all the injustices!!!
    October 24 11:58 AM

    10:37 PM

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