Read the pages in the text concerning isotopes and study behavioral objective 6. The atom , which is the smallest part of an element that still retains the characteristics of that element, consists of , as has been shown, of elementary particles such as the proton, neutron, and electron. The properties and characteristics of an element are mostly influenced by the number of protons present in the nucleus. It can be said, therefore, that the properties of an element are dependent upon its atomic number. The neutron, having no charge, has very little effect upon the properties of an atom but does add to the atomic weight because of its mass.
Atoms of the same element have the same number of protons. The atoms of carbon, for example, all have six protons, the atoms of oxygen all have eight protons. They may or may not have the same number of neutrons per atom. Carbon, for example, ordinarily has six neutrons but may sometimes be seen occurring with seven neutrons. It is called carbon 13. When carbon is found with eight neutrons, it is called carbon 14. Chemically, all three of these carbons behave the same. Atoms that have the same atomic number but different atomic weight are known as isotopes. Write this definition in your notes.
15. The properties of an atom are primarily dependent upon its
- a.) number of protons
- b.) number of neutrons
- c.) nuclear spin factor
16. Adding neutrons to an atom increases its
- a.) atomic number
- b.) charge value
- c.) atomic mass
17. Atoms that have the same number of protons but different of neutrons are called
- a.) isotopes
- b.) polytropes
- c.) ions
Study behavioral objective 7. The number of isotopes for each of the elements is not the same. Some elements may contain many isotope forms on Earth and some only a few forms. Hydrogen has only three isotopes, hydrogen, deuterium, and tritium. Do not be confused that the first isotope hydrogen is the same name as the element hydrogen. All of these isotopes contain only one proton, therefore they all have the same chemical properties. Deuterium contains one neutron and tritium contains two neutrons.
18. Fill in the table below and place in your notes.
| Name of Isotope | Number of Protons | Number of Neutrons | Total Mass of Atom (amu) | Characteristics |
| hydrogen | most hydrogen on earth in this form | |||
| deuterium | twice as heavy as hydrogen | |||
| tritium | radioactive because unstable |
Press here to check your answer.
Draw the atomic structure for each of these three isotopes of hydrogen in your notes. Look at the questions in the previous lesson concerning isotopes. You may want to use the back key to come back to this page.
How many electrons are present in the different atoms?
How are the electrons arranged in the shells?
These questions and others will be answered in the next page. Go
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Last modified October 22, 1997.